She comes to know that Bani's child that was lost in the accident was Pushkar's. Remember that the nurse didn't know who the father was, so she wrote the name of Pushkar Shukla as dad's name when Bani goes to the hospital after the accident.
I think they want to keep Pia as one of main characters and not totally negative, so they might come up with a cock and bull story of how she wants to take revenge on Bani and Pushkar because they cheated on her.
It's only a wild prediction!!