Okay so based off CH 5, she knew that ML was dating MC and that ML likes MC. But she still continued with the marriage, I HAVE NO SYMPATHY FOR HER. She made a choice, she’s not a victim.
And like the ML said in CH 5, “As I thought, you put your feelings before your brother’s, who treats you as top priority. I just wished to receive what I wanted.”
—So in conclusion, I don’t gaf about the sister.