If she went to the police they may have contacted the alleged abuser, and I don't think these girls would particularly care if the man is guilty or not as Muslims are extremely tribal.

Also, it'd be a lot more convincing and a lot more dignified to challenge a malicious accusation openly and publicly with some kind of verbal defense than to gang up on a child. "Mob justice" being Plan A against a 13-year-old doesn't scream innocence to me.