Good question! It really depends on her dementia. Definitely don’t tell her that she “has a memory problem” or anything like that. If you think she’d be okay with it (and some people are) you could say that she’s moving to her new home. But, that doesn’t work for everyone. If she would be upset, suggest that she’s going to a doctor’s appointment, and this is where it is. That makes sense because she’ll be attended to by medical personnel and the staff there. It will take some adjustment, and she may ask to go home when she sees you. Eventually she will adjust and probably prosper there!