Help dealing with family. Is it wrong that I feel that her own daughter should be stepping up to help her mother?

There are reasons why your SIL won't be and does not want to be her mother's caregiver. Mom might have an amazing disposition and be a joy to be with for many people. That very likely is not the case when she is with your SIL. Maybe you and your husband could sit down with her and talk about those reasons without judgment or contradiction about what she tells you.
In many families there is often one sibling who grows up as the family scapegoat taking the blame for everything. The one who is the lightening rod and catches all the anger, resentment, bitterness, the parents ever have. In families siblings don't all have the same experience growing up in the house. Many times there is abuse with one of them and the others don't even realize it's going on. In later adult years it's usually the abused sibling (almost always a daughter) who ends up taking the responsibility and being the caregiver to the abusive elderly parent.
I tell you from experience because I've been living it for years.
Please try talking to your SIL. Let her know without getting heated that both of you are upset and resentful of having the responsibility dropped into your laps without warning. At least get her to turn the POA over to you or your husband. Otherwise your hands will be tied and you won't be able to arrange care for mom or manage it. Please have a talk with your SIL.
If you've decided that you and your husband are going to keep mom at your home and be her caregivers, you have options.
If you want six weeks off this summer and want to go on vacation mom can be put into respite short-stay care in a nursing home or LTC. You can hire a live-in caregiver to take care of her for a few weeks in the home. Don't take the option of a nursing home or assisted living off the table. Talk to your SIL too. She very well might be willing to help out some if she knows that she will not have to have mom living with her. Good luck.

The consensus seems to be that SIL is an evil self serving 3itch, but in my opinion she has zero obligation here beyond dealing with finances.
You say that you are the ones who have watched your inlaws deteriorate for years, why was nobody looking at the long game and planning for the inevitable need for a higher level of care at some point?
MIL needed 24/7 care and you stepped up, kudos to you for your compassion and care. I never tried to guilt my sister into providing any hands on care for my mother because I knew that was not her forte; she couldn't, she wouldn't, and if left up to her my mom would have been in a nursing home 5 years earlier. Nonetheless she was free to visit and interact with both of us in the same way she always had without the stress of veiled hints and overt or passive aggressive accusations because I owned my decision, I knew if it became too much the fault was not hers. Yes, covid has been a consideration over the past year but as others have already pointed out it does not need to figure into your future now that vaccines are widely available. Stop nursing your grievances and start planning the next step, it's time.

You don't mention whether your MIL has any cognitive or memory loss. If not, then she has some say in the matter. You also don't say how old she is or if she has physical limitations. Was your SIL living with your in-laws when your FIL passed away? Was she caring for them in their home?

If your SIL was not caregiving but is the PoA and your MIL is in her right mind or only has very mild cognitive/memory issues I'd take her to the attorney and have her reassign durable PoA to your husband so that he has the legal ability to actually help her. At that appointment I hope she will also complete her Living Will (Advance Care Directive) and her Last Will.

In the end no one can assume or insist or demand that any one person care for another, and your SIL certainly doesn't sound like she's capable of acting in your MIL's best interests. Once your husband has PoA then you can both move forward and not rely on the flaky sister or her "help" or opinions on the matter.

But if your MIL has enough cognitive decline that she can no longer create a new PoA, then that's a totally different answer, so it would be helpful to know what the facts are in your situation.

We need to hear SIL's side of this situation before judging people. Sounds like there is a long backstory here. But it does seem as if OP is expecting SIL to act according to traditional stereotyping of family life, which may (or may not) be realistic in terms on their family history. Of course it should be MIL's monies being used for her care - not SIL's. And POA is not guardianship. Much different responsibilities. Husband has POA too so maybe SIL will resign her joint POA and then let husband take charge. But trying to force SIL to act as a traditional family member is a waste of time and energy.

I agree with Greaton777, if MIL is competent or only mildly cognitively deficient, have her revoke the current POA and assign you husband as DPOA for both medical and financial. I don't know your MIL's financial situation, but it might be good to contact and elder law attorney to get everything straightened out including having SIL provide proof she is acting in MIL's best interest as far as financially.

You can hire in home aide for MIL or charge for your services but that doesn't guarantee SIL will actually cut the check. I don't know where you live, but in my area, SNF, AL, MC were still admitting residents - I know Mom's AL facility would take in new people, only bad thing is they were locked down in their apartment for 14 days. They are now open for visitors after following the protocols. But again getting her into a facility will be difficult if daughter won't cooperate; unless MIL has access to her own accounts.

I also agree there is nothing you can do to make SIL take care of MIL, her "dumping" her at your door 2 days after FIL's funeral says it all. I'm sorry things are strained. Can you and hubby sit down list out needs and wants, have SIL do the same and sit and calmly discuss without a mediator. Otherwise mediation may be necessary.

I wish you and the family best of luck.

"Both my husband and I are not happy that we are stuck with trying to arrange care to get a break when we feel she should step up and figure it out."

Maybe your husband and his sister need to sit down TOGETHER to figure this out...I get you're angry about the circumstances, and you have every right to be, but many of your responses seem to have the continuing theme that you think SIL is the solely responsible party. Has it always been this acrimonious between you and your husband and his sister? Has his attitude about taking care of mom been one of "you're the daughter, mom is your responsibility" - especially since you say he is "uncomfortable" with toileting issues...I'm sorry if this sounds harsh, but to drop mom off on the doorstep with a bag of ill-fitting clothing sounds rather extreme - like an "I've reached the end of my rope" extreme. Did you and husband think MIL was automatically going to become SIL responsibility once FIL passed, because she is the POA? Being a POA doesn't automatically make you the full-time hands on caregiver, nor should that be the assumption made when someone agrees to POA responsibility!

I agree with the previous posters that, if you and hubby are willing to step into the primary caregiver role, then your husband should be the POA. But that very well might be a moot point, if your MIL has advanced beyond the ability to change the POA. If you truly want to resolve this, I strongly suggest hubby put aside the rancor with your SIL, and work with her to find caregiving arrangements that everyone can live with.

Good luck.

If SIL is POA that given her a great deal of authority over moms finances & assets. That she has quite effectively & ruthlessly gotten you & hubs to be responsible for moms day to day living and medical needs shows SIL is clever & cunning. There’s another C word I’d use but let’s not....

Imo as long as shes POA, any solution is at an impasse.
I think your choices are:
- mom is cognitive and competent to handle her own affairs and she does a new DPOA and name you or your hubs as her new one. This you get done at an elder law attys office and at the same time update any other legal that may need to be done.
- mom maybe not quite cognitive and competent to handle “executive functioning” totally on her own, so mom does a voluntary guardianship naming hubs or you to be her guardian
- mom isn’t competent or cognitive enough to do either, so hubs files for guardianship. The elder law atty needs to be one that also does guardianships. It will have costs, but once it’s awarded to hubs he can use moms $ to pay for the costs that y’all will have to front. Guardianship trumps any POA, so hubs will be able to do whatevers for mom, her assets, where she lives, etc w/out Sissy’s interference

It sounds like his folks have a home that is now sitting there empty? Is that it? Are you able to secure the house?
So when FIL died, did he have a will? And is anything happening to open probate related to his death? Any idea if in the will if Sissy is named Executor? If you know this is the case, IMO you need to move fast to get with an elder law atty as he may need to challenge Sissy getting independent administration on FILs estate. Like maybe she stays executor cause it is what FIL intended as per his will but it’s gets done as a dependent administration, so it’s court supervised which means anything she might do to sell or liquidate assets needs to be cleared by the court and mom (or you as her POA or guardian) need to be made aware any asset liquidation or distribution beforehand.

Is Sissy a big personality? Is it that hubs has always tended to defer to Sissy? S MIL scared of the wrath of her daughter? You know your hubs family dynamics best. If so, your atty will be pretty priceless for you as he can take the lead in dealing with Sissy and removes hubs from the emotion of dealing with her. Good luck and let us know how it goes, ok.

Is there something in the relationship between that SIL and her mother that you don't know or don't say here? My SIL (wife of brother, the oldest) would say my mother is a joy as my mother worships my brother and has showered them with gifts and kindness while requiring nothing from them. (Different situation from yours clearly since you are helping.). My mother has scapegoated me from childhood even though I was the only one who protected her from my father's physical abuse (my mother used me as a human shield) and has treated me like garbage despite my being the one who was there for every surgery, financial crises (most were lies to get money out of me who has little), downsizing her without any help from siblings etc. I'm going on maybe too much here. My point is that my mother made me her POA (not in force yet) as I've always been the free slave, while treating me horribly my whole life. If you MIL has treated your SIL as the scapegoat or abused her in some way you don't know about, there may be a valid reason she avoids her mother. My brother too has always been physically and emotionally abusive towards me, so I now know I will never willingly be around him again. Just throwing this out there in case this horrible situation applies and helps you understand your SIL. (Of course on the other hand, she may just be an uncaring person. I almost hope for all of you that it's this latter situation.). If it is the former situation though, you SIL deserves compassion and the right to have boundaries. She will have suffered tremendously.

A few gaps were filled in by your replies. You and hubby oversaw care for a while. You indicate both SIL and husband are POAs. Was it set up as joint or primary/secondary? If joint, husband should take over the finances and medical decisions. No point wasting time or effort trying to convince her to do anything. He should be aware of her income and assets. As someone else pointed out, the time for discussions around MILs care should have taken place before FIL passed. That ship sailed, so now it's time to make the right decisions for her care. I wouldn't rule out facility care - most places have vaccinated everyone, so they should be safer than bringing in help who may not be vaccinated. Facility care will be dependent on her assets and income.

My YB and I were both appointed POAs. At no time did he EVER take any responsibility or even question anything I did to manage her finances and care. NEVER. We were also both appointed executors for the will. The bulk of assets were in a trust, no need for a will, but several checks came in, like the facility deposit plus interest, the 2nd stimulus, and TBD the remainder of the 1st stimulus they cut as they used the previous year tax return. He was asked to decline and did so WILLINGLY - the only quick turnaround ever!!! I've managed everything for the last 6 years, despite trying to include both brothers in decisions.

Dropping her off at your doorstep wasn't a very nice thing to do, both for you AND MIL. No idea what the relationship between them was, but why was SIL involved? Did she take MIL in when FIL passed? If she didn't want to provide care or couldn't, she should've at least discussed it with her brother first. From what you've said, you and hubby were providing care (with some hired help too?) prior to FIL passing. Perhaps she felt that should continue? As far as expecting SIL to take up any slack, don't hold your breath. It is what it is, so unless husband can work with his sister, he needs to make decisions for his mother going forward. Since you indicate her dementia is fairly progressed, I would consult with EC atty to see if there's anything that can be done to negate her POA. Perhaps if asked she would willingly revoke it herself (in writing!) That would eliminate any need to consult with her about assets/income or any other decision about MIL's care.

IF mom's only income is SS, he can apply to be Rep Payee (legally this is the ONLY way one is supposed to manage someone else's SS funds.) Also, if her husband's SS was more than hers, she might be entitled to more. If he becomes Rep Payee, SIL would have no access to MIL's income.

If this is her only income and there are no assets (such as bank accounts, house, etc.), then she might qualify for Medicaid. Depending on her needs AND income AND state rules, that could be facility care or some (limited) in home care. Medicare might cover up to 5 days of respite care IF the person is on hospice. Could she be approved for hospice care? Given your description, she might qualify - talk with her doctor. They also provide supplies and necessary medical equipment at no charge as well as some help like bathing and support for the family.

Is there a house or just an apartment? If house, it could be sold to ensure funds for MILs care, either by hiring help or seeking a facility for her. Another good reason to see an EC atty. If apartment, can you either move what items you'd like her to have to your place or storage until residence is decided?

"...I think she should pay for the respite." "...has the responsibility to step up with help or financially until things are settled. This should not fall on my husband an myself only."

NOTE: POA does NOT put any financial or care responsibility on the person/people appointed. It shouldn't fall on you & your husband, but it isn't her "responsibility" and you can't force her to pay. If MIL doesn't have enough income, it would be nice if children could/would chip in but it isn't required.

You say below that your mil has little to no money. I suggest you apply for Medicaid. They have in-home care programs that would pay you and/or other caregivers to care for her in your home. ( If she was in a nursing home with no money Medicaid would be paying her expenses.) An elder lawyer could advise if you need help through the red tape. Also your sister in law should turn over the full POA to your husband since your mil lives with you. If she won’t, file for guardianship.