Regardless of what it is, one thing you can do for her which can only help any eye injury/ailment is to do a warm compress with a tea bag (green tea). Heat some water, soak tea bag like you are making tea. Test the warmth on your own cheek. When comfortable, hold onto her eye for 10 -15 minutes if possible. Can be done twice a day or as needed.
Green tea has anti-inflammatory properties and it draws out infection and swelling. You can use the tea in the cup to add a few drop to her water bowl as well. I've used this method on newborn chicks (that mama hen pecked almost to death), and 2 other of my chickens that had gotten eye injuries or respiratory problems. Never had infections set in and they healed nicely.
Any suggestions on where to buy the vaccinations? Look like quite a few options online. I only have 5 chickens but i have friends with chickens too in case i have to buy bulk. Is it pretty easy to vaccinate? First timer...