I had a hen whose legs froze up to the knees early in January (She decided to sleep standing up on a negative-temp. night!). She recovered from it fairly well. She was really old, though. She died soon after of old age, unfortunately. It was just too much for her to handle.
The vet said that the best thing to do was to soak her frozen bits in warm water once or twice per day and to put triple antibiotic ointment on any open wounds. I put my girl in the same room as our woodstove. I tried keeping her in a cooler room in the house, but I think that actually was not as good for her (after she had properly warmed up). Her feet swelled up a lot, which may happen to your girl's wing if it's not completely frostbitten. It looks nasty, just hang in there!