Because girls who alter themselves that way are viewed as freakier than talking animals that can command elements~? Who know?In a world full on magical animals which some can speak, why wouldn't one accept one that want to be a girl?
Perhaps Kitten just want to be left alone because that's what kittens do?
Kitten doesn't wanna be left alone tho that her only choice. What she wanna is irrelevant in a world that hate her. So whether it nature or nurture don't matter she supposes, she gonna continue to sneaky around outside with her kitty friends and snipe moneys and Potions so she can get those badges.