The mom and brother are close and he probably thinks highly of her and she spoils him while any real conflict comes from Woori as she tries to steal them down the right path. She’s the only one not smiling, her clothes are more plain and she only has one hand on the chair while her mother also a hand on Woori’s brother’s shoulder. This probably why she doesn’t really care about romantic relationships. She’s been isolated by her family already she probably doesn’t want to start a new one.