its sort of part of her back story, she has an eye just like volleyball (steven universe) but it wasnt for the same reason, she lost her parents in a fire but in that fire she also got harmed in her eye and it got blank, the doctors say its a mystery why she has the cracks but thats why she is always happy, if she gets mad the crack gets bigger so she went to therapys for happiness so she doesnt crack anymore, she covers her eye because she was bullied in her orphanatory da end :>