We are not sure if it was the rooster. He is mean but never did this before.It would be good to put some disinfectant on it, such as chlorhexidene, betadine, or Vetericyn wound spray. Then plain Triple Antibiotic Ointment is very good twice a day until it heals. Keep her separated in a dog crate in the shade until it is healing. Was this done by a rooster trying to grab her on the back of rhe neck or hens? If you can post apicture, that would help.