Well you can't do anything with dirty stuff to work with. She ignores his surprise because really with Chikusa you can't see it anyway if that's even what you'd call his reaction.

"Thanks for nailing Sho." She scrubs cheerfully. Anyone shooting Shotaro with arrows is ok in her book. Though there's still room to change her mind about such things. She looks up at the question staring at the ceiling thoughtfully. "I don't really get it but I remember who I'm supposed to be." Her head drops and she looks at him with a frown and concern warring on her face. "I'm Natsu outside here you know. And Natsu isn't nice." There's probably nothing he can do about it but it's still upsetting. It's one thing to 'play' Natsu it's another thing to be her with real people getting the brunt of her bullying.