She just can't believe that. There's something he isn't telling her. She supposes (wrongly) that it's how to become grown up. Holding the secret over her head. "You don't like it when I keep secrets from you. I don't like it when you keep secrets from me, either. But fine. If you won't tell me how to become the same as you are, then you come back with me and be little again. We're twins. You can't just go and be whatever you want without me," she says, angry and sad and hurt all at once.