I had a little hen get attacked by our big roo while trying to intigrate her into the flock. She had a similar injury and you could see her neck bone. I immediately took her in the house, put her in a tank we had and asked my parents to put some Neosporin so we cover the injury with that and put her under a heat lamp. She came back from the dead and made a full recovery. Maybe you could try something like that. I hope she gets better!