This is Dr. Christian. Some more information will help me help you.
Is it in only one eye?
Is your cat squinting or rubbing at the eye?
Any sneezing or nasal discharge?
Does the white of the eye look red?
There are a few possibilities.
It think the most likely possibility in this case is either a scratch or debris so I would recommend having her checked by your vet. If there is a scratch then pain meds and antibiotic ointments can be given to help it heal. You can continue to clean the eye and flush it with the saline. If you have more questions or concerns please let me know.
Will be harmful to her if I wait until tomorrow to take her tothe Vet?