Board Thread:Questions and Answers/@comment-108.205.136.124-20140225234503/@comment-10458954-20140228032241

It looks like we have an answer (As of episode 20).

The reason her eye didn't regenerate may be due to something along the lines of life fibers not being able to perfectly repair everything. Or maybe if you cut it the right way with the scissor blade a body part won't regenerate.

There's also the possibility that her eye is fine and she's just covering it up for some reason.