Antara knows Maya.
It is highly likely that Maya sought help from Antara in hood faith when MJ exploited her. In her flashback, Antara can be seen comforting Maya & Maya feeling relieved with her support. But then Antara betrayed her on MJ's orders to stay with him. Probably she was the one who attempted to drown Maya in water as seen in Maya's flashback. Maybe she was the one to slap her as well.
Maya will try to drown Antara in water in the party to suffocate her. She definitely wants to create fear in her mind by repeating what Antara had done to Maya in the past. Antara herself has earlier confessed to have done some horrible things along with MJ.
It's just my theory. Antara definitely isn't any bechari character, neither iS Diya. Both women have done some really shady things in the past & are fearful of the past coming back to haunt them. It's a different story that MJ's mothet who is vocal of her apprehension with everyone doesn't show resentment for Antara. Infact, she sides with Antara more often.
It will be interesting to see layers of every character unfold in the upcoming episodes.
Thankfully, they showed a different flashback today of Rudra which sheds some light to why Rudra hates MJ and finds himself incapable of loving anyone ever again.