Refusing any activity; any suggestions?

If you have a nice big window where she likes to sit you can set up multiple bird feeders. My MIL w/short term memory issues (who also stopped doing a lot of things) really loved watching the birds and animals. Many nursing homes have finch aviaries and fish tanks.

Ask her if she would like a ride. Like to play a simple matching game of any kind. Does she like radio. They get tired. For my Aunt she liked to just sit and look out the window. Told me when she thought of anything much at all it was her life and all the good times she had. She said she was content with that. Don't expect her needs to be what you might imagine your own are. I do think if they can get to any day groups where there is activity and other folks, music and art and whatever, it is very good, esp the socializing if this was someone who loved socializing at all.