Preteens and teens are a lot like politicians - they are famous for changing their minds. Tell her how impressed you are with her work and that she finished the project. (Most of us still struggle with that one!) Then smile and let her try other things.
Remember you introduced her to a hobby. If later in life, she returns to it, then take that as a compliment. If later in life, she ventures in other directions, compliment her and her accomplishments.