So I have three hens, two hens live together in the coop and another one I had to separate because of a major flesh injury of unknown origin a few months ago. I'm aware that chickens get excited by blood and they will attack sick/injured members of the flock. I isolated the injured hen and she's physically healthy (aside from poopy butt) but she still lives by herself in an enclosure away from the coop. When I let all of the chickens out into the yard for "recess", there's no immediate aggression from the bully hen. When the bully and the isolated hen happen to walk near each other, the bully attacks, pecking out neck feathers and the comb. The isolated hen clearly doesn't learn and keeps wandering into the bully's path and I always have to be outside to supervise them. I thought that if they hang out more everything would calm down because they used to live together not long ago. FYI all of the hens got along until one of them got injured.