Here's where I am thinking Mitali comes in as the supposed third angle, Mitali has had feelings for Neil and like some of pointed out its been ten years so maybe she thought there could be hope for her. Is it realistic that she would wait ten years? Well it all depends on when she came back in the picture. Basically the way I see it they could go with Mitali having feelings for Neil and being outraged that Neil could still love Avni after such a betrayal, she could feel Avni does not deserve Neil or doesn't know his worth. I don't know I am speculating here since we are unaware of how she fits into the picture, we don't even know what has Neil stay back since I am sure Avni would win the competition. Everything is speculative at this point but its a possibility how she fits into things and adds to Avni's guilt because no one knows why she did what she did.
It is going to devastate Avni to know how much she hurt Neil and it is going to be equally devastating for Neil to see that Avni killed the traits that made her who she was. It is why I look forward to how they get through this and heal each other, will it happen after Neil learns the truth or before? How will he see how much she has changed and how will he revive that side to her? This is what holds the potential the whole possibility of third angles, the poor acting by Mishti and catalysts to the story can take a back seat when there is so much promise that awaits.
Do you think there is a third angle b/w Metali and Neil which will accept by both and Hanse Neil will move on