Good on you loopyc.
i reckon worst ways your get a caution from the police, tho as other post have pointed out, she may thing twice as you and the school are aware of her behaviour.
I can't stand bullies, and yes i would defend my children even if it meant hitting someone, i believe in dealing with it the diplomatic way, but every so often you come across a parent who's just come of the jeremy kyle show, and the only language these people no are either abuse or violence, well with me they will meet their match in any such way they wish, i'm not gloryfying violence, but sometimes their is no alternative