I have no experience with this particular condition, but I am glad that you are trying to find a way to help this lady.

When my uncle was in a nursing home, he loved to tell people about his past, so I would often ask him to tell me a story again--and again, and again. His roommate loved to tell about the small business he had run, so I would often ask him about that. One lady who had dementia perked up whenever there was a music performance. She would sing along and move her hands to the rhythm. Her daughter told me that she used to love dancing, but now she was in a wheelchair. Another lady with dementia and also in a wheelchair never went anywhere outside her own room without her purse on her lap. I noticed that one visitor gave her mother a manicure about twice a week. As I got to know them, I found out that the mother had been a beautician who had her own salon which the daughter now owned. It is amazing what gives comfort to different people. I hope you find the things that help your mother-in-law.