This video has proven to be pretty popular on Youtube. There have been a number of comments stating that -- given her well developed style -- she's clearly not a brand new smoker.
I think that's right. It seems clear to me that this girl has been doing it for a little while and a good number of cigarettes have passed between those lips. I think the video tries to capture that moment of realization that she's flat out hooked. No possibility of denying it to herself any longer ... she is encountering the dramatic lifestyle adjustments of the full-time smoker, and all the private regrets that come with developing such a foolish habit.