If I ever saw something like that I would legitimately charge with nothing but blind fury powering me.
Always hated bullies but seeing someone getting ganged up like that was always one of my sore spots due to getting the same treatment when I was young.
if she was just the victim of bad luck or it was the playful messing with friends do (like how you talk shit to each other and such), i could handle her treatment better but outright bullying is fucked up and, while it might be an extreme stance, i feel that anything less than zero tolerance enables bullying and if you enable it, you're no better than the bullies. the worst i had was being called names by one kid in elementary school so i had it better than most (though it pissed me off to no end), however i have an ex who still freezes whenever she sees her bully from middle school and its been almost twenty years since she was bullied.