I'm betting she'll be fine. I have a golden Campine named Kitty Cat who had her right wing torn off. Unfortunately, when we tried to find a vet to help us nobody treated chickens. The only "advice" we got from one vet was to "put her down if she's that hurt, it's just a chicken." That was when she was about 3 months old. She will now be a year old in September. Chickens are tough. Kitty Cat doesn't act any differently from the other chickens. You'd never know she was missing a wing. So, at least your girl still has her wing, but even if it loses function she won't be any different. I hope you find what attacked your girls. We never did figure out what happended to Kitty Cat.
Here's Kitty Cat
Just so you know, that picture was taken on the side that she lost her wing. You can't even tell, can you?
Here's Kitty Cat

Just so you know, that picture was taken on the side that she lost her wing. You can't even tell, can you?