The way she manipulates her family by playing the victim and then bullying them, and how father and son have had to tiptoe around her to avoid her breaking out into one of her moods. Joon Young found the body in the first place because he’d rather go to school early than listen to his parents fight, and their fight (at least what we heard of it) was mostly her making herself into the victim (”I want a divorce” and “maybe I should just die then”) while Dad tried to get her to calm down. She blames all her troubles on her son. Her response to the news that Joon Young was going to be in the trial was to try and destroy his things, and it didn’t look like it was the first time (which is backed up by the fact you could hear her destroying something breakable in one of her previous fights). It wasn’t exactly a healthy reaction (anger, yes – the destructive way she went about expressing it, no). Maybe she has a good reason for treating her son like dirt beneath her shoe, and maybe she is genuinely sick with a physical ailment, but I feel like she must have some sort of personality disorder, perhaps on the borderline spectrum.