Sounds like it is bad enough where you should go to pinless peepers. Put it on the ringleader first, if that doesn't stop it put on all of the bad ones. Your poor girl needs a chance to heal and they won't let her. I would put the worst offender in solitaire (crate _ for a few days to take the starch out of her sails. Any that dare to take her place, would be isolated also. I think you really have to come down hard . Isolating the victim is punishing her. She didn't do anything.
I think taking the worst ones out of group for a few days will confuse them enough where they may let her be. But would still get peepers for them to drive the message home.If they have something else to think about (peepers) they won't have time to bother her.
Meanwhile check victim often, to see that no flies lay eggs in her wound. Maggots can do horrific damage much worse than what she started with. BTW maybe a hen apron would cover her rear a bit, to help it heal.