I agree with Sourland and Casportpony on it looking like a bad case of fowl pox. Casportpony has much experience with severe cases. Look inside her beak and throat for any yellow patches that might be signs of wet fowl pox, a more serious form. Since you have had MG in your flock, and since MG can be one of several bacteria that can cause secondary eye infections, I would get some antibiotic eye drops such as cipro, from your vet, or Terramycin eye ointment from the feed store. It won't hurt to give her Tylan 50, just in case, but fowl pox itself will not respond to antibiotics, only some secondary bacterial infections. Tube feeding her could help keep her alive until the eyes can see food again in a few weeks. Or if you cannot tube feed right away, at least wrap her in a towel, and try to get her eating a wet mash of chicken feed, egg, a tsp of plain yogurt,plus water to make it runny. Do this at least 3 times a day. Let us know how she gets along.