Here's the point. The young lady is now being harassed at school because her parents found the video on her phone and they posted it. Had they not done that, no one would know this 11 year old at all.
No, she's not the moron who filmed the incident. I would take her phone from her and go through it to see what else might be there. I would delete anything I felt inappropriate. Thus the punishment.
I still blamer her parents. They should have immediately gone to the authorities with the video.