Naaah, I dont think Jassi will slap Purab. To slap a person publicly, that person should generate that kind of an emotional response in you , be it love or hate. Jassi has been comfortable around Purab, not a constant emotional live wire as she is when around Armaan.
Moreover, the way Jassi is behaving nowadays, I would be happy if she says a word in favour of Armaan publicly.
I don't think she will or should slap him, but she can and must confront him verbally.
She has been working hard towards a plan and Purab knows about it too. He's aware that she called GM folks in the party on purpose.
I don't know much about that scene (Purab arguing with Armaan) other than the promo clipping, but if Purab was taking his personal grudges out on Armaan, then that was uncalled for and unfair to Jassi/Jessica.