Dont spray blue cote on an open wound. It is to harsh. Use something healing and sticky like salve. Triple antbiotic cream or niesporin. This will keep the flys off.- Peach had a wound and missing feathers on her wing and down to her butt feathers. M
You may have to put your hen in a separate cage while she heals as the other birds will peck at the wound.
Small chicken hawks are a threat to full grown chickens by the way. I had one that would kill a chicken a day. Eat a small amount and the birds were left to lay in the yard. Of course he could not move it.
free ranging has risks.
I am glad your missing hen was found ok.