How about tickets to a production (an affordable one, maybe the Junior Theater) of The Nutcracker?
A charm bracelet with a dance related charm, maybe ballet shoes (find out what type of dance she does) maybe a car, maybe a heart, maybe a Christmas tree. There’s a bunch of charms on This Site for dancers including ballet, tap, the word dance, gymnast-style dance etc.
On This Site you can design your own water bottles. Maybe you can make one for her car with a romantic photo of the two of you together, or a picture of her pet or her doing a dance routine, or something else that you find meaningful.
Or a Custom Photo Book
I like the idea for a coupon for a romantic picnic somewhere. Start figuring out where you want to have this picnic and then go to someplace like Whole Foods and start checking out the selections in their cold deli. If you don’t already have a cooler, buy one or borrow one from a friend. Your “date” can be whenever it’s convenient for the two of you, but figure out what you want to eat first. You’ll want sandwiches (which you can make yourself, or buy at your favorite sandwich deli, I love Capriotti’s Sandwich Shop, they even have vegetarian turkey sandwiches!) then you’ll want one or 2 small side dishes like couscous salad with cranberries and walnuts, or red potato salad, or chicken salad with quinoa, grapes and almonds. Whatever you like. They’ll come packed for convenience in Small Plastic Containers Maybe some fancy olives. Don’t forget about the gourmet chips, a dessert like brownies or giant chocolate chip cookies with macadamia nuts, and a couple of bottles of fancy soda like these ones from Izze Sweep her off her feet with your romantic surprise and knowledge of good food : )