The thing here is, that the mother WAS lucky she didn't get a sentence.
because then she would have left 3 young kids to be looked after by a family member, or the state. Would they be better off then?
Look, I get it, I really do...after years of this behaviour she snapped, but honestly, it makes her no better then the bullies, it makes her worse, because she is an adult who should have known better. She has made the bullies into victims.
If she had been hitting her own kid, they'd be no remorse.
When people say "I'd do anything" for my child they obviously don't mean it and I don't say that in a judgemental way. I wouldn't kill for my child. Because then I'd be locked up & what fucking use am I to my child, locked up? I'd rather be with my child, helping her, than locked up with even less power over the situation. You're a fucking idiot if you think killing for your child will end any kind of grief, end any kind of upset, because all you will be doing is giving them ANOTHER thing to contented with, only this time, they will have to do it without YOU!!!
If you want to add to your child's pain, be my guest, but don't have a dig at those of us who wouldn't do so.
And saying you don't mean it in a judgemental way doesn't take away the fact that it IS judgemental!
I'm tired of people on MN perpetuating the very actions we complain our kids have to suffer from But that is EXACTLY what you are proposing & supporting here....you are condoning this woman's actions & saying it is OK for her to beat a child, but it isn't OK for the child to beat her daughter...
I'd rather become part of the problem And what of your already struggling child when you are in prison?
Not one of the pro-violence to bullies on this thread had thought through the consequences of their tit-for-tat crap. Exactly..I said it before...hypocritical much?*
But I won't let anyone harm my child, and if violence is the only way to stop that from happening (which many posters have proven is sometimes the case) then so be it. Don't harm my child, but I can harm you.. 
I doubt it to be honest, because otherwise you'd have more empathy So just because she isn't yelling support from the rooftop in favour of violence, she hasn't experienced bullying etc? Wasn't it you who criticised finnbarrcar for calling out the op for not sharing her opinion, yet you have just done the same, criticised her for disagreeing with you & called her a liar to boot? Why accuse her of lying just because she doesn't agree with you? Not everyone's experiences are the same, doesn't mean you are allowed to crap all over hers just because you don't agree with what she would/wouldn't do did/didn't do!
The little shits are even going to get compensation And whose fault is that? The person who hit them, because by doing so, she turned THEM into the victims. Which is why it is never a good idea to fight violence with violence!