Does anyone else feel guilty about getting disgusted and angry?

Mom is in her late 90's and amazingly physically healthy and never gets sick. But she is almost deaf and has dementia and a lousy attitude. She shouldn't be living without assistance. The doctor says it is not bad enough and won't give us a letter which would tell the independent living facility that she is not mentally capable of living there. The truth is, she is incompetent, absolutely exhausting to be around. We considered forcing her to move, but she would make our lives hell if we did. So, for eight years we have soldiered on, doing everything, shop, clean, laundry, finances and monitor her behavior, etc. because she isn't capable of making decisions, doesn't bathe, barely eats and does nothing but complain. There is plenty of social activity at the facility, she isn't interested in anything. She won't help herself and wallows in self pity. Yet, she is more spry than residents ten years younger. She abuses her body with laxatives (which she continues to buy at the facility store, hides from us, and weekly we hunt for them and take away from her. I finally figured out what is happening to her underwear which keeps disappearing - she is having leakage (no longer uses pads for it like she used to - increasing dementia) and sometimes pooing her pants. Then she just tosses them in the garbage. (Mainly from the laxative abuse). Because of the dementia and a 3 minute memory, although we have told her 100 times, she continues self destructive behavior and we can't be there every minute to stop her. I feel bad that she is old and depressed and I know its partly the dementia (she cannot responsibly take any medication) but I have to say, she has always been vain, self destructive and miserably negative about everything. Now its just worse and more so every week. I hate having to repeat the same things 5 times a day, every day, every week, every month and having to talk at the top of my lungs, knowing she will just forget in 5 minutes anyway, listening to the same complaints over and over and over week after week - its wearing my patience and I find myself feeling angry by the time I leave and my stomach is in knots because getting angry at her wouldn't do either of us any good. She won't accept she needs help, complains and whines the whole time we do things for her, and her favorite subject is inventing things to worry about. She has had a wonderful long healthy (and pampered) life, yet behaves like she is a victim. In fact, I have more health issues than she does, some fairly serious. She's my mom, and I love her, but I feel guilty that I dread going there and can't stand to be around her more than an hour. I don't want to feel that way. My husband said 20 years ago she walks around with a black raincloud over her head. There is nothing we can do but to keep on for years to come until she is so bad she doesn't know where she is. But I am so tired. Does anyone else feel that way sometimes?