Knowing her nature and maddness she can do that and she is a self centered selfish woman who can do anything to keep her status.
Keeping thenknife in Aditya's hand also she can do that she will espace this crime and see how Zoya will save Aditya.
This way she will test Zoya.
She has already confessed to Sakshi she killed Pooja andYash and then dumped Salshi.
Aditya will be for a shock when he gets to know what extend his mother can do.
His dailogue that Anjana his mother cannot do wrong she will prove him wrong and the final nail will be her big confession.