Maybe girls are into vampires because it has something to with menstruation? Vampire blood as a symbol for fertility, sexuality, and being at an age when you're trying to sort these questions out?

Every culture needs/has had a menstruation/fertility goddess image and perhaps vampires are it?

Male vampires have a "blood lust" and that's funny, that's what teen girls have....

Yes, I agree, there's more complexity about vampires here than meets the eye.