You have my sympathy. This situation can really be impossible. I just finished my stint taking care of my 92-year-old mom. It went very well, considering, but it is a difficult situation.
Mom was with us for about two weeks, and now Sister 2 is caring for her at Sister 1's Oregon house until July 3, at which point Sister 3 will pick her up and take her to her Tacoma house until August when Sister 1 will pick her up and drive her across the country (again) to her New York house.
Mom is totally confused about where she is and where she's headed, but it doesn't seem to be stressful for her. Her short-term memory is shot, and she had a little cheat sheet that she kept with her to tell her what was coming up.
It was nice to have her here, and we enjoyed our time together, but I'm relieved that it's over. There was a good bit of worrying about her choking or falling.
Allow me relate three stories:
1. Every night she had to walk up the stairs and every morning come down them. Sister 1 was amazed that she could do this; INAD, but I think it was very good for her.
I would always be one step below her in case she fell, and she'd always say "Oh, don't be silly, I'm not going to fall" but I'd explain that she had fallen in the past, and I was going to do it. The thing is we'd have to have this discussion every single day, since she'd forget about our previous discussions.
2. I asked her if she'd ever had a colonoscopy and she asked "Isn't that what I had the other day?" I couldn't help laughing, but she didn't like the fact that I got amusement out of her memory difficulties.
3. An advantage of the memory problems is that you get do-overs. She asked whether she should write lyrics to a simple song that my group plays, and I explained that we don't have a singer, and we don't need lyrics. I could tell that she was disappointed, and I wished that I'd just said yes. But the next day, she asked the same thing again, not remembering the first time, so I just said, "Yes, that would be great!" and she was pleased to have something to work on.