Well, as a fellow elf, I can tell you that teenage girls are notoriously difficult to shop for. However, I do have a few suggestions that may help you out. First off, if you're not sure what she likes, you can't go wrong with a gift card to her favorite store or online retailer. This way, she can pick out whatever she wants and you won't have to worry about getting the wrong thing. Alternatively, you could also get her something like a piece of jewelry, a new outfit, or even a makeup set. Just make sure it's something that reflects her personality and interests.