You mentioned your hen had a pretty beat up Comb....
is she able to walk correctly?
no swaying? She keeps her head up pretty well? No swinging of the head or "floppy neck?"
I had a polish pullet with similar symptoms, she had a head injury.....
she wouldn't eat or drink by herself.
Feel around her head gently for any abnormality in her head structure, opposed to another chicken of her breed. Make sure nothing is out of place.
Hope this helps you identify whatever is going on, and a big prayer to her getting better.