You could put money in a card but also make a voucher for her to spend some time with you, say on a shopping trip or to the cinema. That way you get to spend time together too and she remembers having fun with her gran.
Christmas does not need to be expensive if you use your imagination. Make your own vouchers can be useful, babysitting service or doing the housework for someone, taking them for a meal, washing the car, anything that gives a break or spends some time together. Even a book of vouchers gives choice, say one a month. Make a gift, paint a canvas, write a poem or a story, do an album of growing up photos, decorate a shoe box and put favourite sweets in shredded paper for them to find.
I've got some small chocolate Father Christmas's and snowmen, some cellophane bags, curling ribbon and thank you stickers (the bags, ribbon and stickers I already had) and I am making up little thank you bags for the deliver people, Tesco delivery men, post lady and my Hermes delivery lady. Only a little something but it's still nice, I think.