Where do I go from here?

My mother was diagnosed 1.5 years ago with ALZ. She lives at home with her boyfriend of 15+ years and has lived there for about 8 years. She has gone off for a walk twice now within the last 4 months. The first time she walked 4 miles to her sisters house. The second time she was angry, left the house, seems to have been walking to her sisters house and a concerned citizen called the police, who were able to bring her back home safe. Lately, in the evenings she forgets her boyfriend is her boyfriend. She knows his name but thinks there are two of him and the one there needs to leave because it's not "her boyfriend." I've had to go over or talk on the phone to try to calm her down. We called the ALZ hotline & they walked us through having her boyfriend leave for 10 minutes and come back. This has worked, but getting him to do this each time is also a chore. It's starting during the day now too and she thinks he's holding her hostage. He recently had enough, and brought her to her sisters late one evening, unannounced & said he just needed a night off. My mother knows this house 30+ years my aunt has lived there. She wandered most of the night between couches and the guest room. Clearly moving her to her house or even my house (which I have only lived in 1 year and she wanders around during the day when over) is not an option. Biggest issue is that she does NOT want to go to a nursing home, so she wouldn't be good in the assisted living setting, but she's too aware to be put into a memory care unit it seems. But what can be done if this continues? I know he cannot handle it much longer.

Utilmately my question is, has anyone been in this situation and where did you go from here? With a loved one that is aware enough to not want to be in a nursing home, but issues with where they currently live.