No I would never blame Jassi for all this.If Purab had asked her 'look I know you love Armaan and are you sure you can forget about him in a space of one month flat and be happily married to me' and she would have said yes,then I would have blamed her.
It's been proven again and again and again that those who are capable of taking sound business decisions with far reaching effects are not so astute when it comes to taking emotional decisions.In fact many mega successful business men and women have their personal life in shambles.Have any idea how many broken affairs Sabir Bhatia has gone through?
If the girl says yes for marriage no guy would ask the question you said. Its a very simple logic and your question is itself answered by the girl when she initiated the topic!!
If the guy proposes the marraige then the question arises for him to ask for girls permission and clear things out, Here the girl is already saying yes, she wasnt not under any pressure.
In short the situation never arises. to ask your question, If jassi hadnt initiated the topic and only her parents had said yes to purab on her behalf, then it would have been right for purab to ask jassi as to whats in her heart or mind. Also mind you jassi was shown very happy with her decision. It was her true happiness which was showing on face. There was no way purab would have guessed that what she is saying someday she might not be happy with it. So the situation was not as you assumed. Jassi initiated the topic and she said yes!!! She also said in the restuarant about her PAST love!!
Jammy.