Chickens can be quite resilient. We had a hen who the rooster and dominant hen decided needed to go. When we rescued her, she had a quarter sized exposed skull on her head from the pecking. We separated her and put a little neosporin on her and she's still with us. She is particularly resilient though, as she's at least 10 years old and has survived when all or most of the rest of the flock got killed by a raccoon raid and twice by dog attacks. She recently was missing for three days and just showed back up with signs of surviving yet another attack (she's the only one who know how and/or has the desire to get out of the protected chicken yard). I wish your girl well.