Many comments including fro urs truly about why Sat is behaving the way she is. She is grey yes. But some points came to my mind.
Was she always like this? They r showing how she can manipulate easily while at the same time show love and affection. Yes she is using Ladoo, but she loves him also. She cares for him albeit not to the same extent she may have done for Vatsalya or even Anami. She has blackmailed the Pathaks, giving Sudha a taste of her own medicine, etc. She is also shown as the intelligent but dominating wife of Baldev whom her FIL trusts more than his own son.
But was she always like this? We will only know if the makers show the past. I don't know whether they will do that. The naive yet intelligent young wife - probably she was like this before she came to know the intricacies of LM; her husband's infidelity and his illegitimate son. Some scenes of the past have also shown her to be loving to her husband and MIL. She was cheated during her marriage. Probably all these factors have made her hard hearted. Also her relation with Dheeru - I wonder if Dheeru's wife and she were related. We don't know. I am not justifying her actions, but I was wondering about these.