It is just my opinion… not to hurt feelings of any one or against anyone.
HD writer is so intelligent and knows the pulse of viewers. So she doesn't want to clear the suspense from their mind. Who will pair with who? Twist around 4. I guess.
Doubt arises here…By the time when 2 incident took place SD was under an impression that RD married Indira. He heard from RD but didn't know that the marriage is incomplete. So his next move ..to create misunderstanding between RD and Indira and deviate the attention of Indira from marriage to scene 2.
Chances are there that he asked Mandira to do this favor and wished the same. As usual Mandira as she can marry SD if she does this for SD might agree for the marriage.
So I guess nothing was happened between SD and Mandira so again the story revolves among these 4 and the viewers continue guessing who pairs with who.
Finally for all this drama, through the court a big lesson to Mandira, for misusing law and wasting the court time by false allegations.
It is purely my guess don't mess it with anything.