A false rape claim? Pretty much without fail, the reason is that she liked him and couldn't have him. It's a form of envy, and it's extremely common. I don't think there's much reason to beat the bushes for a "why do the bad guys hate us?" reason if someone lies under oath. If she did that, she was the sociopath.
Is it possible he was maybe-somehow not a nice person in some other respect? I don't know, and I don't actually think that's any of my business, or hers.
Oh right, good one, uh huh.