Yeah, I'm worried she's run out of local adults too. I honestly would go to the police at this point if only to drive home how exactly uncomfortable she feels but I'd worry they'd call her an over reactor.

Unfortunately other than explaining "I am telling you about him because I feel very uncomfortable and violated why is no one agreeing he should stop?" the only other option I can think of is warning the boy (and the adults) if he touches her again "I will hit you" and then follow through. Unfortunately THAT only works without getting her into trouble if there's an adult to argue that she had no other choices.