Nandini plan could be
1) Make Ram suspicious that even Priya is involved in Akki Shivi kaand, that way Ram will separate from Priya
2) Kill Priya, permanent solution. Ram will be completely under her custody
Shashi plan could be not to kill Ram. He told that to
Mr Sood because he won’t agree to kill his own daughter
so pucca Nandini & Shashi are involved
So during Lohri kaand, Priya will get a call from
Anjali saying that she has proofs. Anjali might ask her to come alone, hence Priya goes in an auto. Ram sees Priya leaving (this was not expected) and follows her. Mahendra Sood else Raj would have caused the auto to fail and hence accident