Not really? She never addresses Dahl's behaviour and let's her do what she likes only meddling when her sister is hurt or sad. She never intervenes for the sake of the victims
Ze truth!
What are you talking about? She addressed Dahye's behaviour about bullying Ayeon and she was suspicious Dahye started bullying which led to her finding Yoonseo. Of course she wants to help and protect Dahye, she's her little sister but she also also doesn't want Dahye to bully others. She didn't threaten Yoonseo to not talk badly about Dahye and was actually kind to her. Yes, she's also thinking intelligently to solve the whole fiasco and have Yoonseo by her side, but she could have been mean, threaten her with violence, abuse her etc like Dahye did. But she was gentle and patient with her. She's both smart and kind.
I think Dahye's sister is my favorite character from this story, she's kind-hearted and caring.