Here is my take. Upset that the pics got burnt yash goes to pub to drown his sorrows. Aarti follows him there. She tries to pacify him but he tells her to leave him alone.
Then Aarti tries to arouse some reaction in him and starts to dance with some guys. Yash pretends to ignore her and shows indifference. Someone spikes Aarti's drink and tries to misbehave. Yash comes to the rescue. He becomes the hero that he already is. Both head home. And in the intoxication they become close. Yash remembers aarti does not.
We can even bring the new guy Aman here if we like.
We can also bring in the diary here which yash could have read in the morning after to find out Arti loves him after unintentionally becoming close could be the betrayal that is eating away yash.
Do let me know what you think guys