Shocking! The Wicked Supporting Actress Does Whatever She Wants With Her Beauty

A Beautiful, Vicious, Stupid Female Villainess and an Upright, Self-Restrained Gentleman

That kind of spoiled, arrogant junior sister who's a concubine's daughter and is useless apart from her looks. She's nasty but stupid, and everyone sees right through her, yet she poses no threat and is more like a kitten. A gentle young master and senior brother who falls for her first and willingly becomes her protector.