How is your girl doing? I just discovered a similar injury under the wing of one of mine and found your thread when I came looking for advice while she enjoys her epsom salt soak. I hope to trim away some of the clumps of feathers and apply neosporin. It didn’t JUST happen, but it’s been in the last couple of days. She’s hidden it well—I only noticed because she had a tiny bit of a limp. It looks like something grabbed her by her ribcage, but I wonder if she could have gotten caught in the chicken wire trying to fly over the top of the run. She probably isn’t going to tell me. 
