A personal card/note or something else that would be meaningful, especially if you've worked with her for a number of years. Those are my favorite gifts. You could get a little something to go along with it based on her likes and what the new job is- something like a coffee or restaurant gift card to make life with a new job easier, especially if it means longer hours. Places that are convenient to her house/job.
Or something fun to give her a break from the new job- just make sure it's something she actually likes! Movie gift cards are good for coaches who like movies, but they're up there on my list of least useful gifts as I'm not a movie watcher. Target and Amazon gift cards are pretty generally useful for most people, but perhaps less personal. My favorite gifts, besides personal cards/notes/pictures, are the ones that show the gymnast knows something about me beyond my life in the gym. So for me, my gymnasts know I'm crazy about my dogs and animals in general, so when they draw me pictures of animals or buy treats for my dogs at Christmas it really speaks volumes to me. So if there is something your coach really loves (books, pets, fancy nails, movies, good food, coffee), go with that.
