Not to give false hope, but ducks can rebound from horrid injuries. She does need your help now.
Ducks have an inner eyelid, a nictitating membrane, and that can get swollen. You may be seeing that.
At this point I would try to get some Vetericyn eye gel, and get her into a clean tub of lukewarm water twice a day - at least once, before bedtime, followed with the Vetericyn eye gel.
Vitamins twice a week to give her a boost, and talk it out with her. I think you both might be able to encourage each other.
I would also consider starting her on oral antibiotics. I am no vet, but perhaps Duramycin - available at many feed stores - is what I would use.