this signing of divorce paper was necessary to answer all questions that Alekh and Sadhna were tied together for two reasons..one after Alekh got normal, he never had any other option than to accept Sadhna, as she was his wife and secondly that Alekh was indebted to Sadhna and hence accepted her. But now that Sadhna has signed the divorce paper, Alekh is set free to decide whatever he wants and whoever he wants...so if now Alekh chooses Sadhna, all the doubts in the people's minds will be clear, Vasu will get a tough answer and a permanent one too...that Alekh loves Sadhna and hence wants to spend the life with her...there is no elemnt of gratitude or backlock in this decision of Alekh...his decision is based on his pure love for Sadhna in the present circumstance...
So here also, unknowingly Vasu did a favour to both Sadhna and Alekh in setting them free and make them their decision, whatever it might be...realtionship has to be two-sided...with Sadhna, Alekh has to also feel that same feeling....only if Vasu knew that she is doing this favourđ...she vut the branch on which she is sitting