I have a friend who works in a catholic facility in Sun Valley. She "adopted" one of the residents as her "BFF - best friend forever"
I noticed that the best friend, despite of severe dementia, is always up and about. The staff in that place has given that resident a baby doll for her to take care of.
It has given "BFF" a reason to get up and face the day because she has to take care of the "baby doll"
The staff has been great in greeting BFF with her "baby" and going along with the play.
Maybe you can try introducing something as a reason for your mom to get up and about.