So she's just a very strange foreigner.Now that she has used magic he can no longer excuse her being a chuunibyou elf cosplayer.
These days I hear cosmetic surgery is quite popular with young people.I understand since he is a teacher, he probably thinks he is dealing with a kid with chuunibyou syndrome. Though, the ears alone should already have given away she isn't a human. (touch them and they would feel real instead of fake ones cosplayer use).
Now that she has used magic he can no longer excuse her being a chuunibyou elf cosplayer.
she a tsundere, I expect by C50 at minimum she'll realize a bit of what she's feeling XDAgain her with her "heart condition". She'll learn one day.