Distracting from anxious behavior. Any suggestions?

I'm asking if anyone has any suggestions for me. I help care for my husbands grandma. She has Dementia, but has a long history of depression and anxiety. She lives with her daughter and son-in-law (my inlaws). I come a couple times a week and help my MIL with her care and once a week I stay with her all day while they get a break and run errands. Every time they are gone for more than a few hours she starts to worry and she is convinced that they are never coming home. She will obsess about this all day. I know, because of her Alzheimer's that reminding her doesn't matter to her as she will forget almost immediately after I tell her they will in fact be back at a certain time that day. I was wondering if there is anything I can do for her to get her mind away from that. She doesn't really like games or anything. I try to do some activities with her like simple card games or folding towels, but she usually gives up in the
middle of it. All she really wants to do is eat and watch tv. Any suggestions would be appreciated.