With Christmas ahead -what can one do for Christmas in a nursing home?

Keep it simple. Activity of any sort will be stressful for her and you. Maybe visitors one at a time throughout the season. Don't make it overwhelming for her.

I doubt it will matter to her. Get her a nice card and be done with it. The home will have decorations and events.

How oriented to time and place is she, do you think that Christmas will even matter to her? No doubt the nursing home has holiday activities planned, although I actually wished there was a way to opt out because I felt it was a painful reminder of what we had lost (I'm pretty sure that was not how my mom felt though).