Online pet pharmacies sell fish and pigeon antibiotics that we use for chickens. Most don't require a prescription. You can also find these at Petsmart and other pet stores. If you have a pigeon supply store, those meds work splendidly for chickens.
The only roadblock you would have is if you...
Continue to flush the eye once a day and twice a day, put Neosporin in it until you get the terramycin, then use that twice a day.
If her behavior becomes lethargic, she may have a respiratory illness and an oral antibiotic may be necessary. Keep her separate for now in case she has a...