I've been trying to think of a way to put this that doesn't sound like I'm agreeing with them, but I'm going to try.

Some fourteen-year-olds with really intense crushes on older guys want, or think they want, to have sex for whatever reason. Maybe she thinks that's what relationships are, maybe there are other issues in her life, maybe she's been molested already. It happens. But whatever's going through her head, that does not mean she really understands what's going on, that it constitutes informed consent, or that the older guy can say 'she wants it, it's okay.' It's not okay, and it is the responsibility of the adult in the situation to gently reject such advances if they do occur.

(I'm still not sure if I'm making sense - I just remember being a fourteen-year-old with really confused ideas about relationships, sex, and marriage, and if I hadn't been quite so painfully shy, it's not at all a stretch for me to think that I would have tried to initiate something like that with one of the older guys I crushed on.)