It looks like ocular Mareks disease to me as well. She looks like shortly she will need to be kept near food and water to find enough. A wire dog crate inside the coop with the other chickens would be good. Place her own food and water in there. I would eventually try to get a necropsy performed on her when she passes away, just to confirm Mareks. It can have implications on whether your flock will all be carriers or not.

