Hi there! My name is XXXXX XXXXX X would be happy to help you with your question.
Is the discharge coming from the same eye as it was previously?
There might be a concern that she has developed a similar infection as before. If it's an abscessed tooth, she will need oral antibiotics to get rid of the infection. If it's an infection of the eye itself, she will require an antibiotic ointment for there eye to help get rid of the infection. Since it's also localized to one eye, your vet might wish to stain it to determine if she accidentally lacerated it.
Unfortunately, there aren't any over-the-counter medications that can help with that. However, you can help reduce the irritation in her eye by gently flushing it out with lukewarm water, or the ocular sterile saline you can buy at the drug store for contacts.
If you want to flush it out, I wouldn't use salt-water, I'd use the saline formula for contacts, since it's far more gentle. Similarly, plain tap water can work just as well.
Green discharge usually indicates an infection, but on the off-chance that she's experiencing irritation due to allergens, you can try to give her plain Benadryl at a dose of 1 mg/pound of body weight every 8-12 hours to try and reduce the signs of inflammation in the area. However if the irritation isn't caused by contact with an allergen, it may not help. However, it likely won't hurt her, either.
Benadryl is very commonly used as an antihistamine in dogs.
You are very welcome! I hope Shelby gets to feeling better soon!