You're not wrong, but it's a realistic one. Winding someone up to the point they snap is on both people. You'd not get pissy at a dog for snapping because someone was pissing it off, people should be held accountable and be able to exercise better patience, but we all have breaking points and can only take so much. She was also in physical pain from it, that alone can make people lash out defensively. If you've never been so angry at someone trying to annoy you to the point of lashing out then you've lived a sheltered life and not been much of (if any) a victim of bullying behaviour. She couldn't easily remove herself from the situation without getting in trouble, teachers are notoriously shite at dealing with stuff like this, she asked the person to stop being a twat, they didn't they got twatted, that's on the person being a twat.

Soo you get 5 days off of school AND make some dickhead think twice about kicking your chair again? Awesome. This is the correct and final way to deal with bullies. I regret not smacking mine in the mouth sooner, it tends to work.