Comment by Zay on Yes, It's Me. The Obsessive Side Top - Chapter 65

@Zay right?? Shouldn't she blame her husband for switching the sons lives

@Zay She did! She is just a bad person. She believes only her first son and herself are the victims of her husband foul's play, but it is obvious that Hajin is a victim too. I guess that is all about power play. Since she can't win nor fight against her husband, she went lower and start doing it with someone obviously weaker and maleable. 
At the end of the day, she is just as bad as Hajin's father.