It is a very good question- whether Gunjan was right or wrong?
Mayank was already going to marry Charu but the question is after finding the truth would he agree to marry her. The problem is Mayank does not care how many people he hurts with his change of mind and how he is playing with Charu's feelings. I get that Charu was manipulative. But no matter what she cannot be used and dumped as per his mood swings only because she is crazy about him. He is certainly taking advantage of her. And like it was discussed before here, what was Charu's parents fault in all this?
I think Gunjan made a wise decision to ensure this marriage, that was already half-way, finished properly. Knowing that Gunjan has backed off, Mayank would have left in anger and hoped that he can change Gunjan's mind in future. But now he has to continue and stick to something that he started
. I am glad that Gunjan forced him to do the right thing by concealing the whole truth.