I don't understand this character at all. I get (even if I don't agree) what her problem is with Katha. But if she doesn't want Katha encroaching into her space and family, why is she not encouraging Katha and Viaan's relationship??
Her riling up Viaan's mother against Katha is going to make Reet's life only miserable. It would have been more consistent with Reet's character to show that her thinking is that "The only way to put some distance between Katha and my family is to distract her with some new man". She is shooting herself in the foot by playing Viaan's mother against Katha.
The writers of this show are otherwise very smart about human emotions, but this inconsistency always annoys me.