Do you have room for another coop/pen
With my flock we have personality conflicts so I have to have 2 coops and 2 pens. I rotate when coop gets to roam the yard and which stay locked in the pen for the day. (you would think with 5 acres there is enough room for 17 roosters and hens to live comfortably without fighting, but I guess we need to go out of our ways a try to kill each other)
also what breed is this bullied hen (because could be the bird's problem? polish don't fight much mainly because they cannot see as for trying to find friends, same with silkies