Okay she can not return after the five year leap if she was jailed for the murder as it is 14 years and Bajaj would not leave her because of this knowing that she will get released he would be their .
Now here are some of the possibilty
Prena finds out what Bajaj did to break her and Anurag relationship
Bajaj had a small hand in orginal Prems murder
Prena has a sickness and decides to leave
Prena religiously has to leave for happiness of her family
She realize her love for Anurag
Bajaj suspects her and Anurag relationship
Bajaj has an afair
Any ideaS?