Could you post a photo of her and her crest? Is she with any other birds? The bad crest feathers could be caused by feather mites, picking by the other birds, or molting. Without seeing a photo, and if she was my bird that I was showing, this is what I would do:
1. Give her a good bath to remove dirt, parasites, or loose feathers
2. Pull out any feathers which look particularly bad. They may not grow in completely by the show, but a sparser crest is better than a full, but raggedy one.
3. Dust her with Sevin dust/another mite and lice spray to remove parasites. Clean out the coop or cage she is in, too, in order to get rid of more mites/lice.
4. Keep her separate from any other birds until the show to prevent picking.
5. Feed her sunflower seeds and/or mealworms until the show. The higher protein in those foods will help her grow in new, pretty feathers.
