Dobby is eventually, at some point when she's entirely over Mark and Mark is not entirely over her, going to write the drunken gay porn story of Mark and Jeremy's love while giggling over it with her friends (possibly one of those IM sessions that gets out of hand) and accidentally email it to Mark, who's going to have a panic attack that his possible-latent-bisexuality that he's forgotten about has leaked out so much that everyone can see it, and seems to be focused on Jeremy. He will then get horribly awkward and weird around Jeremy, who will attempt to resolve the problem by giving Mark drugs of some sort. This will lead to sex, which, much to Jeremy's frustration, will lead to even more awkwardness.

And you're a much nicer person than Mark. Or Jeremy, as I've only seen you do good things out of love and/or general niceness, not as part of a duplicitous ploy.