Sadly. It's an awful story which could have been a lot worse. God knows what these two girls were thinking of.
Often, when kids sexually abuse other kids, it's a sign they've been sexually abused themselves. I'm guessing the spotlight may now fall on one of the families. Or both. Or maybe one of the girls holds an undue influence over the other. Maybe they're just bad'uns. Who knows? It'll all come out in the wash. It's just another sad sad story.