At the end of the day, Mohan has lied to his family and to Kastur about his degree etc, sometimes you have to be hard to get the truth out or clear up misunderstandings (also like when Mohan told Kastur he never loved her on 2 occassions and he was blunt and to the point) and in this case Kastur had to clear her doubts, put her love to one side and look at the man who has with honesty said he has completed his degree to her and everyone because this questioning of his degree will continually come up, Mohan will keep on denying denying like he has since they married and Kastur should really have pushed questioning Mohan when his degree was questioned by the shop keeper and she did right today, people wont like the way she did it but it had to be done, after reading and watching today's epi, all I can say is sometimes you can just sense and feel when a loved one is/has and is still lieing to you and that to your face, then seeing their facial reactions and the way they deny it, you sense it and I felt that Kastur must have sense and felt that too, that is why she didn't believe Mohan because he has not been honest, whereas Kastur has always been honest that is why Mohan always believed her. Kastur had a doubt about Mohan's degree and this is the second time its being questioned and that by Sia being Mohan's bestfriend, Kastur said she didnt believe her or the proofs are faked by her but the Homewreckers smugly and confidently revealed Mohan's truth, she has nothing to gain nor loose. Sometimes you have a gut feelings and sometimes its right, this is my personal point of view.