I had a duck suffer some pretty bad wounds on her lower back. I don't know what caused it, but it was under her wing and I didn't even notice she was injured until after the maggots got into it (very hot summer days). It was an awful mess, but we cleaned her up and moved her into my shop for some tlc. We cleaned and treated her twice a day or more... it scabbed over, the scab came off and there was clean pink skin! She grew her feathers back and was perfectly normal after that. I probably wouldn't do that for any other duck, but she was my favorite and I was glad to give her more time. She was very tame, loved to eat worms out of my fingers and would follow me around when I weeded to "help" me. I'd say there is good hope for your girl and encourage you to care for her, although her damage sounds worse than Silver's, I was SO surprised at how well Silver did.