I have to agree with @DobieLover when she says your chickens are seriously overcrowded in the run. Rule of thumb is to provide 10 sq feet per hen, so your run should be 170 sq feet, not 25. How big is their enclosed coop, where they sleep at night? They need a minimum of 4 sq feet per hen in the coop. 17x4 = 68 sq feet. We don't tell people these things to be critical, but to be helpful, and to problem solve. If this hen is getting beat up and your facilities are too small, it is most likely that overcrowding is the cause of her troubles. She's a subordinate hen so she's the one the others are going to pick on. They need their space, and the only way they can get it is to evict somebody. And she's the one that's not fighting back.