Kidnap her siblings to get her attention. She's obviously not interested in you right now and this is a quick way to get that attention.

If she doesn't have siblings, slip some sort of non-lethal poison into her soup. When she's not at school for an extended period of time, spread the rumor that she sucked off the big flamboyant senior(there's one in every high school) and told him she just wanted to practice giving head, but instead, wound up with a minor STD because said flamboyant kid sleeps with dirty guys in porn theatres(according to Tom Hanks in Philadelphia).

Last time I checked, though, girls don't find it a turn on when you have to use a message board to try and profess love to a girl in a pitiful, desperate, attention-seeking way.