If she has a family member or a friend who she sees every day, invite her and her friend/family member to have dinner at her favourite restaurant.
Everyone likes good food and I'm sure she will appreciate your kind gift.
Look at what she uses every day, then buy her an upgraded version of it. That's the easiest way of coming up with gift ideas.
You see her writing with a pen often? Buy her a beautiful pen. She often uses hand cream? Get her a luxury bottle of hand cream. She uses glasses and cleans them manually? Get her an ultrasonic glasses cleaner. She happens to like tea a lot? Buy her some tea from a fancy brand. And so on.
I think she would be happy.