If she is the kind who loves to read then you can also gift her a book that you think she might enjoy. Book of her favorite author or writer is a good option. If she loves cooking then you can even buy her a nice cook book and relish the recipes she makes.
Choclates are loved by everyone and if she is the one who does have a sweet tooth then you can buy her a box of her favorite choclates.
Another option is to gift her a hamper basket. You can add flowers, choclates, a wine bottle, a book or maybe even a small pup that is if she loves pets and wrap it up all nicely.
These are just some of the ideas that you can pick up to buy a birthday gift for her. Hope they help you decide what to gift her.