When my Dad's mother, my Nana, could no longer take care of herself, the responsiblilty of what to do fell on my shoulders as the rest of the family is gone, dead. My grandmother was in the hospital and wanted to go home. We all knew that going home was something that she definately couldn't handle anymore by herself. She was adament and I didn't want to put her somewhere she didn't want to go. So, with nurses coming in and out throughout the day, she went home. I lived right next door to her so I could help too. There were nurses there all day, every day except between the hours of 5:00pm-8:00pm. Nana said she was fine with this. Pretty soon, I'd start getting calls around 5:15 or so. Could you come over and bring me a glass of cranberry juice? Of course I could and I did. I stayed with her until about 7:30 or so and she'd tell me she was getting tired and I didn't need to stay, she was ok and I would leave...both of us knowing that a nurse would soon be there to help her up the stairs to her bedroom. She didn't want to ask for help or to say to me that she didn't want to be alone so I didn't ever do anything to make it seem that way. We'd vist about the day, play along with a game show on television or I'd write out her bills or whatever. It didn't take long before she got tired of all the people in and out of her house and she talked to her doctor about living in a nearby nursing home. It was her decision and she still felt as though she had some control over her life. She lived there for a little over a year before she died. I believe that she was happy while she was there and I think that because it was her decision, it made all the difference in the world.
I know this isn't possible for lots of people but it is how it worked out for my family. I was incredibly fortunate that the nursing home was less than 3 blocks from my home and I saw here nearly every day (I walked by her window everyday on my way to and from work). I was a pain in the ass to the staff when necessary and saw to it that my Nana (and her roommate too) were well cared for.
About being angry and cranky....absolutely....be prepared for it. While I agree with Susan that you just keep on loving them and hug them tight, sometimes, for my own sanity, I would just leave. I would say something like: Okay Nana, it was good to see you today. I'll be back tomorrow. Or sometimes, when she was REALLY nasty, I'd say something like: Nana, you are being really hurtful and I'm going to go home now. I'll be back tomorrow. I love you. And I did go....once I left her room, I cried myself right out the front door of the nursing home and up the street to my house. It was SO HARD for me to do, but Susan is right, there comes a point in time when you realize that you DO have to take care of yourself.
I don't envy your position. Be gentle with your Mom and with yourself...