Why is her hair transparent? Well, I can kind of see what the artist was trying to achieve with the visibility of her right eye behind the fringe, but it doesn't really work. The hair looks too thick to reveal that much behind the fringe; it just ends up looking semi-transparent.
I think that semi-transparent hair looks cool, but weird.
Also, it seems likely that the eyes were drawn first, and then the hair was added later.
Also, it seems likely that the eyes were drawn first, and then the hair was added later.