I concur that you really shouldn't drop it, deposits are for if the customer flakes - not the artist! You were more than patient with her, and if she decided she doesn't want to deliver the product to you - she doesn't deserve to keep any money. If she wants money back, SHE can sell what progress/materials she has.

Don't drop it, threaten small claims court. I know I would be pissed if I got screwed out of that much money.