When I got my hen Nevada (RIR) she was a stray and had a swollen sinus and wounds all over her back, of different stages of healing. I am guessing those were from mating. I took her to the vet, and she thought it could be mycoplasma, or it could be swollen from trauma. She was tested for mycoplasma and 4 other diseases and all came back negative, and the eye cleared up in 2 days. So it could be trauma on your girl too. As long as she's separated already, maybe give it a day or two and watch for other symptoms of respiratory disease, and if it's trauma it should be ok( or improved) in a couple days
