M.A.
I think that the most appropriate gifts within the work world are ones that stay within the work world. Such as a personalized office item. I don't know what kind of work you do or what kind of work environment this is, so I will give several ideas that could workd in different settings.
You could order some personalized stationary, such as notepads, sticky notes, etc. With something like "From the desk of (her name)" You could do it cute if she is that kind of person and you are in that kind of work environment, or simple and professional if it is a more professional environment.
If it is more of a professional environment, a really nice pen with her name engraved.
Something personalized for her to hang on the wall in her office.
I often think that in some work environments, giftcards, food items, clothing, basically anything that they would take home is a little questionable, but again it really depends on the work environment and the relationship.
Another idea is some kind of monogrammed something for her office. I don't know if it is the kind of office that has a couch in it or something, but a pillow or blanket to go on the couch in her office. A leather file holder with her initials momogrammed on it.
Books are always an appropriate gift if chosen well.
Just ideas. If you were more specific about the work environment I think we could all give more appropriate suggestions.