My Mom is accusing me of mistreatment and being very aggressive. What to do?

I have been her primary caregiver/POA and I'm devastated. I am the eldest daughter, with one sister. I have always been the primary caregiver to my mother who is now 87. I have noticed decline but have helped her gently and been her 24/7 concierge, making sure not to shame her for forgetting, etc. She has faulted me for seeming "rushed" and, conversely, for doing too much. I can't seem to win. I quit my PT job to be more available to her but then she complained that I do too much.

We have had a difficult relationship. I am the daughter of a narcissist, but thought that I had come to terms with that and that age would mellow her. It is quite the opposite. She expects people to bow before her.

I just take a deep breath and keep my eye on the prize which, to me, means doing the right thing and care for my mother. If she has a need, I fill it. If she has a question, I try to find the answers. If I see a hazard, I fix it. I have put my own needs to the side.

Two weeks ago I was setting up her voicemail and asked her the birthdate of her late husband (my father) needed for a security question. She flew into a rage and threw a phone book near (not at) me. A few weeks earlier, I was trying to solve an identity theft issue and asked her for her credit card to speak with the customer service agent. She slammed it in front of me. Again, I took a breath and just dealt with it.

Recently, however, I couldn't take it anymore and told her that I didn't deserve this kind of treatment, that I wasn't the enemy, that I was trying to care for her with love and an open heart. She said that I mistreat her, etc. It broke my heart because it's not true. I told her that I was not able to do the things she needed doing in a way that pleased her so I would find others to do it. I found an administrative assistant and a lady to water her plants. I have stayed away from the home since that day, other than to do some work on the outside creating an earthquake kit

I have been working on preparing an earthquake kit for her home and have told her that it is sufficient for 2 people for 2 weeks. She asked me how much I owed her and I told her that she owed me nothing. The next week she went out and bought duplicates of everything I had put in place, cleaned out a garden shed (I don't know how she managed to do all the lifting) and said she would be keeping "her" supplies in the shed. She also dismantled all the safety gear I had put in place (gas and water shut off tools, flashlights). This is such aggressive and discounting behavior.

I have POA and have recently been made co-trustee but I don't know how to effectively perform these roles now that she has made me Enemy #1.

I am single and have no one at home to express my grief and confusion to. My sister, who lives an hour away and who has spent years telling me that our mother has not been a good mother, is acting in a "holier than thou" manner instead of offering any support or participation, siting her own declining health.

I have been reading obsessively about the aging process since the recent blow up occurred and understand all the challenges that our elders face. That is why I have been treating her with such care and compassion.

She has made a mockery of all that I have done, discounted me, and this is bringing up old wounds from childhood.

I am feeling physically ill, cannot sleep, so depressed, so confused, angry, etc.

What do I do now...?