She may have been injured and got an infection, so either way the saline, ointment and antibiotics will help her. When she heals up, I would bring one of your other hens into the house with her. Let them bond and then put them back out with the flock. You may have to do the playpen method (cage her in the coop so the other chickens can see but not touch) for awhile, maybe with a buddy, until they lose interest in picking on her. My large flock, fourteen of them, have been in a 33 x 25 area of the pole barn with our alpacas since november. In order to keep them busy, we give them a flock block, and scratch twice a day. They don't pick on each other at all. 3 roos and 11 hens. I think chickens get bored easily, and your little hen may have made an easy target. If you have to keep her and another hen inside until you have grass outside again. Maybe the flock will be so busy they won't notice her. If you can see which one is bullying the others, separate it for awhile to knock it down the pecking order a bit.