Don't kid yourself
No 12 year old could match my wife's enthusiasm for Harry Potter. She has all seven books basically memorized. Trying to watch one of the movies with her is an exercise in frustration. She either rants about what they left out of the movie or says the lines right along with the characters.
The silver lining is that her enthusiasm for all thing Harry Potter has kept her from getting too deep into the world of sparkling vampires.