I would also consider - since it's warm, may be infected - either oral antibiotics or slather triple antibiotic ointment (not the kind with pain reliever, that is toxic to ducks) around the base of the bill.
I would put some apple cider vinegar in her water (if her regular water dish is galvanized metal or aluminum, switch to stainless steel or plastic so metal won't leach). I would go with a teaspoon per half gallon for a few days and see if that seems to help.