There are chances that she might know the truth. Its not possible for nimmi to hide the truth from her in all these years . After the leap i never saw her questioning nimmi or even herself about the truth. Even when surbi was questioning everyone about the truth she was not supporting her nor there were any signs of curiosity on her face to know the truth of why being treated like this. She was behaving as if she knows the truth and has submitted to it well before.
I think apart from surbi everyone in the house knows about the truth. Thats why surbi finds the chudail thing ridiculuos.
What do u guys think??