She knows niharik'a truth and she'll never abandon Ram...Its all part of her plan...she has given a small victory to niharika so tht she gets overconfident and makes a mistake.
This separation is just temprory Priya is not stupid.
Niharika is very cunning if she can malign Krishnaji's image in front of 20 year old Ram she can do anything...its not easy to malign a mother's image infront of her own son...children fully trust their mothers...Priya is not typical dumb soap heroine she has brains.
Priyas need to do proper planning before exposing Niharika...and leaving ram is 1st step to it.