"Arnav blurts out the truth... ofcourse knowing Arnav's character, he will not allow Khushi to explain things. Even if he allows he is not going to believe her version. So more anger and hatred brews...
Later, Shyam might kidnap or try to do something with Arnav. Khushi will be of great help in spoiling Shyam's plan... there might be an encounter of Shyam and Khushi again and this time all the truth comes out of Shyam only and Arnav witnesses everything.."
See from all the previous happenings.. its a known fact that Arnav lacks in co-relating capacity. There had been so many instances where in he had felt how haste he was and made a mistake in blaming Khushi. But never once he was able to co-relate it with the terrace incident. He couldnt clear his mind that why cant even that incident be one of his false assumptions.
The point is the terrace scene is so very etched in his mind that only something similar intense encounter between Khushi and Shyam can erase that one.
Just jotted down what all i felt ... thanks!