Looking for support and guidance in dealing with my mother.

I have been reading stories and comments on the forum for several days and I think you guys are amazing. I am hoping that maybe some of you can help me. I'll try to not be too long-winded, but I need to give you some background regarding my situation. I am dealing with my mother who is 77 years old. She has COPD and is on oxygen. We have a strained relationship to say the least. My father to whom I was very close, died by suicide in 2002. He had been in the hospital and was quite ill. The night he came home from the hospital, he ended his life. That is when this whole drama with my mother started. I thought that I was doing the right thing by moving her into my home with me and my husband. At the time we lived in a small modest home that was plenty for my husband and me, but with her living with us, we needed a bigger place. I suggested that if she could help out with a down payment on a bigger place she could have her own living space. She then told one of my brothers that I was trying to steal her money. After my dad died, she made me POA, so I had access to her finances, but I would never do something like that. I was very hurt by the accusation. Since my dad was no longer alive to buffer her behavior, I began to see who she really was. She is downright mean and nasty. She was always manipulative and tried to pit me and my siblings against each other, but now it became increasingly worse. I now know that she has a personality disorder. Since we couldn't get along, I moved her back to her home. She stayed there for another 2 years before I moved her into an independent seniors apartment community. It is a real nice safe place and there are lots of opportunites to socialize with people her own age. Even though she has access to everything she needs (meals, housekeeping, hair salon, etc) She still expected me to do everything for her. I never did anything right. She called me at home up to 7 times a day to tell me how she needed this or that done and how depressed and lonely she was. If I happened to not answer or not be at home, she would leave nasty angry messages on my voicemail. I was a nurse for 17 years before I became a homemaker. I do not have children, therefore she thinks that I should be at her beck and call. Trying to be everything for someone you can barely stand is exhausting. The guilt, anger and resentment is sometimes too much to bear. She knows exactly what buttons to push to get a certain response. "If you were a mother you would understand" and "You should take care of me because I am your mother and think about all I sacrificed for you." I wanted to have a child very much, but I couldn't. "So and So's daughter takes her to lunch every week and has her hair done ." She has alienated everyone where she lives because she is so mean and hateful. She puts on the charm at first always complementing them etc. She always puts me down and acts like her children never do anything. It doesn't take long for the real person to come out and then no one wants anything to do with her, but she is always the victim. I really like a lot of the older folks that live there. They are always pleasant and cheerful and remember me when I visit. They realized a while ago who the problem is. In 2009 my brother died by suicide. If things were bad before, you can imagine how much worse she got. Last summer I ended up in a psych hospital with a complete breakdown. After years of banging my head against the brick wall that is my mother finally took its toll. It was the hardest time of my life, but I learned so much about myself. I had been trying so hard to make my mother into the kind of mother that I needed my whole life. I wanted a relationship that she was unable or unwilling to give. I finally set boundaries and decided to make my own happiness. I cannot make her happy and I most certainly cannot change her. It seems so simple, but I am just figuring that out. By doing everything for her, I was enabling her to be the way she is. At this point she needs assistance with grooming, but she refuses to allow me to hire home health. She will not allow the housekeeper to clean her apartment. She refuses to have meals in the dining room because no one likes her. I buy one month's worth of groceries at a time for her because she will not eat in the dining room. She refuses to go to the hair salon that is downstairs because she says she cannot go by herself. I recently had to go through another round of "I know you're stealing from me that is why you won't talk to me or help me." I am so tired of dealing with her. I just want to sever ties, tear up the POA and move on with my life. My remaining living brother is so done with her too. He lives about 2 hours away and has not been to see her in over a year. I don't begrudge him his space. I wish I had that as an excuse to not deal with her either. Am I being selfish? I cannot force her to do anything she doesn't want to. I have tried so hard, but I am tired.