The vet took a xray, chickens are often great at hiding pain. SHe could have cancer caused by marek's or she could have had a stroke that left a little off. If it's neurological she wont necessarily die, as long as she sleeps on the ground and stays out of harm. If you let your birds free range...
Is there any chance she might have something neueralogial?
Does not sound like Marek's. My birds never lasted over a month, because it progresses to cancer. They would be very lethargic and mopey. The falling and eye discoloration might point to something else. It's surprisingly common for...