Can you separate her inside your house? If not, and you don't think it is a respiratory infection, then leave her in the coop. It's always good to keep a dog crate or have a space for a hospital for sick chickens. Get some 50 injectable at your feed store, and a couple of syringes and needles to withdraw the medicine. Give her 1cc or ml twice a day ORALLY for 5 days. That way the other chickens won't get unnecessary antibiotics. If you see any white or yellow gunk in the eye, it needs to be cleaned out with saline, QTips, tweezers, and cotton. Otherwise the eye ointment won't help. If your feed store only has Tylan 200, you can still use it, but only give 1/4 cc or ml.