Does she have any sneezing, a bad odor, rattly breathing,or wheezing, or nasal drainage? She could have been pecked in the eye, but a sinus and respiratory infection such as MG (mycoplasma) or coryza may be to blame. Can you try to remove any pus that is in the eye with QTips, tweezers, and cotton balls? Flush the eye with saline. Then apply an antibiotic ointment such as Terramycin. She may need some Tylan or oxytetracycline if she has a respiratory infection. Read about MG and coryza here: http://edis.ifas.ufl.edu/ps044
If she has MG it is very contagious and more than likely all your birds will have it or carried. It can be passed to other flocks. May want to have tested so ensure it is not MG. We went through this with our flock two years ago and just now are back on our feet and MG/MS Certified Clean by the State of Kentucky.