The thing is this stuff happens in real life and shows like Beyhadh 2 try to bring that to light. Yes, it disgusts some, but that is often because of our morals and values and our upbringing. It's also an extension of what we've seen in society. This show is still not as disgusting as some of the things that happen in society.
And honestly I don't see it as disgusting. Maya is using Rudra to get back at MJ. Yes she may have had a relationship with MJ (I'm not going to accept it until they show us the full past story) and may have been pregnant by MJ, but that does not preclude her from getting into a relationship with Rudra now. In my view that was the past and this is now. It depends on how Rudra views it.
Of course, in my view, Maya does not deserve this relationship now and that's because she is no longer just taking revenge, but turning into MJ herself. Killing Rishi, an innocent life, to get back at MJ for killing her child is not okay on my moral compass no matter what. And thus there is no longer any redemption for her.