I am not very familiar with ducks. I do know they need a clean water source to dunk their heads into often to keep the eyes and nostrils clear. Could she have been pecked in the eye? Does she have any signs of a respiratory disease, such as mycoplasma (MG?) I will tag @Isaac 0 and @Miss Lydia who know ducks well, for help. You should also post this on the duck forum here: https://www.backyardchickens.com/forums/ducks.42/
Can you get some Terramycin eye ointment? before trying an antibiotic if she isn't having any other symptoms. Like @Eggcessive said deep buckets or bowls for washing out eyes and nares is important too. Also rinsing out the eye with a saline rinse just in case something has gotten under the eyelid and is causing this.