I haven't seen the film, but I've heard a few people talking about it. This is what I imagine the story to be like.
Humorless, Brooding, Emo, Vampire Douche and Slutty, Vampire Chaser Dingbat get together like everyone always wanted. She wants to have some kind of bizarre inter-species romp before she becomes a cold soulless creature of the night. He's all like, "No, we can't because I will basically beat the shit out of you with my hands and vampire dong." She's all like, "But that's how I like it." He's like, "Ok, but it's going to be bad." And she says... "Ooooh, yeah... I love it bad." He's like, "No, I don't mean bad-good... I mean bad-bad." And she says, "Yeah... bad-bad... that's what I like, have you read these books?"