Looks like a mild allergy. If the discharge is watery, then you can just make sure you occasionally wipe the eye with a clean cloth and maybe start an anti-allergy/anti-histamine syrup if it persists.
If the discharge is yellow, and the eye lids stick together and some crusting is there, again wipe gently with a clean cloth and then a topical anti bacterial eye drops maybe applied to both eyes.
Also, check if she has a cold or any rashes and if anyone else in the family have the same issue.
Good she has no fevers or bowel issues.
Health Tips
make sure your hands are always clean and cloth/cotton is clean when you wipe.