Have you got photos of yourself with her, or places you have visited together? That will give you topics for conversation, and you can leave them with her.
Perhaps some cards, envelopes and stamps and offer to write any messages, or help her to, on her behalf. When I was in hospital for long spells, I became very anxious to acknowledge the gifts and good deeds that were done for me and my family. A friend who understands me helped me by bringing in pretty cards. I wrote brief messages and she did the addresses and posted them. It felt like a weight off my mind. Really, just ask your friend if there are things like this you can do for her?
I am visiting a terminally ill friend soon and didn’t want to take flowers or food of any sort. Any ideas of a little something that I can take to cheer her up a bit.