Isn't Kusum the same girl that cut her wrists when she saw that her groom was not Saras? Isn't she the same girl that taunted Kumud and challenged her and wished her to return to somebody like Pramad just so she, Kusum could have Saras? Isn't she the same witch that put her room on fire to blackmail her sister and later winced when she saw Saras comfort Kumud? And the same girl that was concerned about the "dhoop" and about the family and Saras hating her but never about what her sister was going through?!
Now THIS girl, having done all of the above things AND more, found out yesterday that her sister and Saras were just playing with her and pretending to teach her a lesson. What do you think SHOULD have been her reaction? It should logically have been of anger and hatred and revenge. I'm completely taken aback to see a repentant Kusum!! Doesn't make logical sense.
So it's either bad writing - just like the bad writing that had initially turned a sweet, loving, caring little sister into a witch. OR... is it that Kusum is just pretending and is planning to strike when it will hurt Kumud and Saras the most???!!!