How does she behave when you silently move your hand toward her face? Does she react at all to visual stimuli in her vicinity?
I don't know ducks at all, but compared to chicken and human eyes, it does look normal. Blue tinge around the edges (iris), but the pupil looks clear to me in the photo.
The little bit of blue is normal especially on ducks that are buff, fawn and white or just plain white because they have lighter eyes. I agree her eye looks clear from the picture. Is she acting blind at all?