I agree with Rick. Any sort of "spa" treatment would be a great idea. After all the hard work and self abuse of dieting/training/lack of rest before a show, a relaxing spa treatment would probably be appreciated. Flowers are nice but this (spa treatment) would make it more about her. But then again some people don't like the spa. Just a thought.
I'm sure she'll like what ever you do for her. After all, it is the thought that counts.