Lawdog and Pete F are both right.
It was creepy and unsettling to watch an adult be absolutely impotent in the face of a misbehaving child. That is utterly and completely backasswards.
I expect that this child is not beaten at home. I expect that she is ignored. I used to work with these kinds of kids, and the ones that had been ignored were the ones who acted out the worst. She knew that there were going to be no consequences of any significance to face for her actions. It is a cry for attention. Unfortunately for kids like this little girl, she has come to see any attention as good - whether it is positive of negative in nature is irrelevant to her. Consequently she is brat and out of control. THe folks need to take her in hand before society is forced to do so.
They should videotape this kind of situation (if feasible), physically extract the problematic student from the classroom (if the situation is that extreme), place the kid in an empty room set aside for just such a situation, place a faculty member to guard/safeguard the kid, and have the parents come pick up their now expelled child. If the parents can't won't come pick them up, leave the kid in the room until they get there at the end of the day. Still no parents or guardian to pick up this little gadfly? Call the police and have them take over the situation.
And when the parents try to sue the school system... the Judge ought to tell the parents to go poop in their hat, and fine them for allowing their child to be so disruptive/destructive in school.