The best you can do is follow Wyorp and Eggcessesive suggestions for tx now, and just mindfully observe her and the rest of the flock - which it sounds like you already do. If you begin to see some more serious symptoms, the eye worsens or any other birds show similar symptoms, check back.
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If her behavior is fine, there isn't much you'd want to do. If her eye progressively gets worse and continues to change in color, then you may want to consider treatment.
So at the least it could be an irritate eye. At the worst, it could be ocular Mereks. Not nearly as bad as the neurological mereks, but will eventually lead to blindness. Really hard to deduce from the pics, but here is an article for you to browse and read some up for yourself...