Make sure the coop ventilation stays good, no dust, ammonia odor, or dampness. Offer her a little dampened moist chicken feed, in case the dust in the feed is causing irritation. Probiotics or a small spoonful of plain yogurt a couple of days a week won’t hurt. Check to see if you can get any of the antibiotics listed above, to have in case she has more outbreaks. Tiamulin is pig antibiotic and the others might be available for fish or pigeons. Many countries are very strict about antibiotics now.