She forgets almost everything, misplaces items and even worse, accuses my father who is her primary caretaker of cheating on her. He is 84 and she is 81. She refuses to have anyone help in the house. And my Dad is too emotional to do anything but what she wants. Who and where do I go to seek help? I have a feeling she will have to go into a nursing home, but I know that both of them would never agree to it. What she is doing to my dad borders on abuse. Dad allows her to do it, so it is a never ending battle. She has always had high peaks and low valleys of emotion as long as I can remember. Now they are more frequent, and very unsettling.
Since my mom not only had the behavioral problems and some physical problems, I decided she needed to be assessed at Geri Psych and then go to AL. (My dad can care for himself but was not keeping up with mom’s needs)...but separation seemed a good idea. And it has worked very well. Things are calm and my dad visits my mom every other afternoon, acting like it was 1950 and he was courting my mom.
Assuming she will still be under the care of her cardiologist, that might be a good place to report changes in her mental or emotional state and ask for further, related investigations. I agree that psychiatric and neurological specialists will be helpful sources too, it's just a matter of keeping everybody synchronised so that you don't end up with a whole overwhelming list of recommendations and opinions, some mutually exclusive!
I also agree that your father will feel better for realising that sometimes to help your loved one best you have to do things that they don't at first sight agree with; and I'd add that you could encourage him to appreciate that he deserves care and support too.
If she is being abusive to your father, consider that calling Adult Protective Services, or having her taken for an involuntary psychiatric workup might be appropriate.
Sadly, paranoia is often part of dementia. Has your mom had paranoia as a symptom of her mental health issues in the past?
Of course your dad is sad. But does he see that there could be help for her conditions?