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A victim or alleged victim going to the cops or school administrators about this would be protected speech, meaning its almost impossible to sue her for the activity.
You'd have to prove the accusation was made with "actual malice" - meaning in this context the accuser knew it was false when they made it. Unproven, meritless, speculative accusations to police/university authorities/etc are protected.
Unless there are text messages or facebook or something similar about her faking it, its a non-starter. Moreover, in practice, lawsuits against regular joes like some random cluster b girl in a club are almost unheard of because they have no assets...they just declare bankruptcy, the end.
It certainly sounds like malice in this case. He repeatedly shot her down, then she got payback making a false claim with lots of witnesses to corroborate his side based on what he posted.