I'm loving all the ideas here. Always on the lookout for small gifts.
I think your idea for the the table toppers is great. I would make them coordinating rather than matching.
These are some chenille potholders with coordinating towels that I recently made for a friend. I love the chenille look, as it's quite different from most potholders you see.
Chenille potholders and dish towels
Have fun making something for your sister. That's quite thoughtful! Great to be thinking ahead, too.