Anything related to the series. Maybe order a wand or the time turner, something like that. Perhaps order candy from the online stores! We have a candy store in my town at sells Bertie Botts Every Flavour Beans. They have a bigger selection online, I'm sure. You could also get her an awesome Harry Potter cake if you don't mind shelling out a few extra bucks. Go to your local bakery and see if they can't make something.