Ishana is conning Om out of helplessness however messy may the reason or portrayal of character be. But Riddima is conning Om left right and center without any helplessness, it's purely for her selfish reason. Unknowingly Ishana is saving Om from a fake relationship which would break him in future. He trusts, admires and respects Ruddima's fake personality without knowing the truth. But he admired, got connected to Ishana's true personality on those stairs. Ishana may be conning Om, but while doing this she will mostly present her true self to him which he will fall in love. Her intension may be conning but her feelings and support for Om will be true but it will be diffucult for Om to seperate the fake mask from true face when Ishana's truth of being a conwoman reveals.
All in all Om is getting conned by both Ishana and Riddima, but what stands out is which con is fake and which con is real. When the fake con is unmasked there will be so much realness and love. When the real con is unmasked there will be so much of selfishness and betrayal.