I think she could improve if you keep the infection under control, but the question becomes "Is it worth it?"
The way I found BYC was when a hen of mine was ripped apart by a hawk. I thought it was a fatal attack because I found parts that should not belong to a living bird. Imagine my horror the next morning when I found the bird very much alive and horribly disfigured. BYC helped me to save that bird. She had been flayed alive- no skin from neck to tail, completely bare down to the muscle all across her back and sides. She survived the initial injury, 2 secondary infections, and 2+ months of isolation in my basement. Once she healed, her flock refused to take her back, so she had to be re-homed for her safety. At that point I made the decision that any bird that presented with injuries of that magnitude would be euthanized. My poor bird suffered horribly trying to heal, and once she healed she had lost everything but her life anyways, so was it worth it? I bet she didn't think so. She never was able to fully integrate into her second flock. She was the dominant hen, but always stayed somewhat apart from the rest of the birds. She was killed in a second predator (dog) attack about a year later.
I have often thought since then that I did that bird no favors. I saved her for selfish reasons. I wanted to prove to myself that I could save her, but I didn't consider whether or not I should.
You need to make your own decision about what course you are going to take from this point forward. No one can ever say you didn't try. Unfortunately (or fortunately) some injuries are just too great to heal. And even if they do heal- what kind of life can be had after?
Good luck, Elise.
