The only thing I know of that causes that white cottage cheese looking stuff in the eyes is coryza. Coryza also comes with a very foul smell. You need to seperate her from the rest of the birds. There is a way to treat it with anitbiotics but I cant remember which ones. Im sorry to say but if it were me I would just kill the chicken. Coryza is very contagious and is a pain to deal with. And when you are done clearing it from your flock you may end up with some birds that are carriers and will give it back to your flock again.