Feather plucking questions

My black australorp is plucking the butt feathers out of one of my light brahmas. It's only the one chicken going after her. Blukote doesn't work. This chicken just has it out for her.
So far I have been quarantining the plucked hen, then today I locked up the australorp to give the brahma a chance to roam.
My question is...should I consider getting rid if the injured hen, or the bully hen?
I will consider the peeper eye shield, but if I can relocate, I'm going that way for sure.

 

I started giving them some scrambled eggs yesterday and I'm going to get them back on mealworms starting tomorrow. I'm hoping its a protein thing and not a behavioral thing. The australorp is a good layer.
It's been an hour and no other hen is even looking at the plucked hen, so it's confirmed, it's just the bully hen and no one else.
My husband and I are considering a portable addition to our chicken tractor for more space.