Responses
i think bcoz she was only a child and was feeling insecure of how to become an actual part of the family. they somehow grew up like siblings and felt like she doesn't deserve being part of them especially Byul being so beautiful and what does she have?
About the telling part, she was always the person that was ask regarding Byul since she was the only family Byul have amongst her peers and the only other kid at their homes. She doesn't know what's wrong with telling what's new about Byul, she thinks there's nothing wrong with it. But when she met Byul's boyfriend, she knew it was a sensitive topic and she holds back telling it to her parents.
Lwk guys I would hate having this girl in my life as a cousin, like imagine there's someone constantly competing with you and telling your parents things you don't want them to know, even with her telling the school he was having a baby sibling, that was none of her damn business