It's disappointing that Heejin didn't get even a smack, but I guess it fits, she beat the shit out of his family so he did the same. She's definitely the type to play the legal system as well so in the end it's probably the smarter choice.
Also I'm sure having her brother turned against will her with mess with her more. Since she can't bully with impunity because her bro is no longer top dog at school.