Don't forget to be sure to give her terrific faculty evaluations -- or whatever your school calls them. Nurses (and students) so often forget to do that sort of thing well. They'll buy a present, but forget that the person they want to thank has a career that needs to be supported. By giving your instructor a great course eval, it will help her in a professional way that is important for her success, job securtiy, promotion, etc. It only takes a few minutes to give that kind of input to her supervisors and it provides a meaningful and lasting benefit that can improve the quality of her career and personal life.
As for a physical token of your appreciation ... I would stay away from knick-knacks and other things that are of not much practical use (unless you know for a fact that she has a collection or special affection for a certain type of item). Teachers (and other career women) collect lots of that kind of stuff over the years and after a while, it just becomes more clutter than needs to be disposed of.
If she is a clinical instructor, she is probably grossly underpaid and could probably use a gift that would give her (or help her pay for) something she might struggle to afford. For example -- a gift certificate to a book store, or a spa -- or even a general gift card
-- along with a nice note and a few flowers, a candle, a gourmet treat, or something like that. The "little something" is pretty and brings an immediate smile to her face ... and the gift card lets her buy something she needs or wants, but may have trouble affording.