Only when Ragini comes to know what Vasu has done, the misunderstandings between the 2 sisters will be cleared up.
I think Sadhna will give up or lose the competition and either sign the divorce papers or ask for the divorce papers from Vasu when Ragini will overhear. This is how Ragini will come to know the true face of Vasu.Then, they may show that Ragini will withdraw (on the pretext that she joined late) and Sadhna will win......
thats the best to happen, or else Ragini 's character can never be redeemed.