Um it's called story development. Since she's Taesoo's ex she plays a big part in it. Mmkaythxbainow.
Indeed, she does. But the story would be so much better if the author at least tried to make us empathize with her character in a convincing way instead of demonizing her (yeah, sure, she had it tough, but I didn't really see a real effort to make us like her, she is not even compelling, just hateful) By consequence, is not very exciting to read the parts where she participates. That is not how you do a good character, let alone a good story.
And there are a lot of forced plots too. Like, RLLY YOUR FRIEND THAT KILLED HIMSELF IS THE FL DAD? SO SUPRISING.
i really wish the autor would stop focusing in (that lil fake bitch) a couple we are clearly not rooting for. She is not even trying to do we like the lil blondie more, nor like this shitty couple more. It makes really unexcited to read. The story was SOOO much better in the beginning.