As far as I am concerned, she is a manipulative, evil woman. She could have done the honourable thing and walked away when she found out that Bani and Jai loved each other, but still she continued pursuing him. She could have forced Jai to tell Bani in a proper way that she was pregnant, but she chose the worst, hurtful way for Bani to find out.
Love is a two sided thing. Sure, everyone though Bani hated Jai, and she is to be blamed for some portion of this. But Jai has always been very clear about being in love with Bani and not wanting Pia, she should respect that and move on.
Also love is wanting the person you love to be happy, whether it is with you or not. If Jai is happier with Bani, and if Pia really loved him, she would let him be with Bani.