The step-sister
Sam later learned that the Banks had a daughter of their own, Kitty, who was a year older than her. But instead of finding in her a close friend and a confidant, Kitty gave Sam the cold shoulder, much like Cinderella’s step-sisters.
According to Sam’s post, Kitty’s treatment of her had gone from bad to worse. Mostly, she had her own things going on and she just ignored her new step-sister.