think this way: since she is your dearest daughter, you should know her habits and preferences very well. In fact, no matter what, don't think too much first, your gift is for her!
I think you should consider the following aspects:
1. Based on your understanding of your daughter, does she have anything she particularly likes, but her parents have never bought it for her?
2. What are her fixed habits? Start with her habits, just right, and have a clear goal. It must be something she likes and can use!
3. If you want to give something more innovative and commemorative, then it is a customized gift. Now there are many places that can customize such gifts in different styles. You can provide your daughter's photo and customize it, or you can engrave what you want to say to your daughter on it.
4. Does your daughter usually like gifts, or gifts that she has always longed to have.