Sometimes she was blackmailed by Suraj, sometimes she did it on herself. She manipulated him with the abortion to come and stay with Imli and protect the baby. Then she deliberately came closer to Suraj in front of Vivaan to make it seem that she has moved on so that Vivaan doesn't leave Imli.
We overlooked Vivaan's pain, back then, because we wanted Chakor with Suraj, but he was suffering because he did love Chakor and he was merely a victim of the circumstances. He had no fault at all that Imli had her fun with Suraj and Chakor chose to risk their marriage to do the swap.
What Suraj is doing to her is what she did to Vivaan. She sacrificed their love to save Imli and her kid. She lied to him and manipulated him to save Imli and her child. Yes, she was sacrificing herself too, but she did it on the behalf of Vivaan.
We can tell ourselves that now they are married and in love, but Vivaan was also in love back then and nobody cared for his feelings, not even Imli. She should have not agreed with his sacrifice in the first place: accepting to live for a lifetime with a girl that you don't love just to raise her child with another man is a big sacrifice. Imli should have walked away from this marriage in the first place without a special invitation. But she chose to stay and took advantage of Vivaan's good intentions to save herself and the child.