I will this time only blame kallu for entire scenario. First of all when it comes to.aayi and pillu she becomes too illogical and decides not to involve malahr most of the time. Yaar the moment she knew about sampus truth she should have revealed it to malhar or she knew surrogacy was happening then also she should have called police or malhar and done something to stop it or atleast should have delayed the procedure till he comes. Even now no one knows sampus truth knowing how dangerous she can be kallu has still kept her and how won't malhar think it is not his child beacuse even yesterday she reminded him that surrogacy need to be done with sampu ( despite knowing truth why pretend so and remind him too).
Then the moment fake rachit called she should have secretly said that to malhar she had enough chances either in hospital or at night or while in vehicle he is an ACP damn it he knows and he has protected both maayi and kalayni many a times. She choose to handle that herself .
Malhar being malhar would accept her he won't ask for Agni paroskha instead he will be extra supportive for kallu but just think of the pain that he will have to go throigh when he may feel that she is carrying a child that is not of his.