Trim away feathers near the wound and take a closer picture. Do you think a raccoon or other predator did this? Was it during the daytime, and are your chickens locked up at night? Saline 2 tsp salt dissolved in 1 quart of water (or 1/2 tsp per 8 ounce cup,) can be used to rinse the wound with a syringe or spray bottle. After blotting it dry, apply some plain triple antibiotic ointment on it twice a day after cleaning the wound. Is she able to walk around okay? Are the others pecking at her wound?