The author says they were in the snack aisle and she was "begging for cookies". I read the reference to her weight as a clumsy way of implying that the girl's parents were giving in to her demands instead of teaching her what the snacks cost.
As a hook for the article I thought it was clumsy and unnecessary.
It's even more odd juxtaposed with the "a blue-collar type."
I think it's reasonable to say that this introduction suggests a middle class snobbishness towards the lower class. The worry is that by not teaching the kids correctly, the kids will end up in the lower class.
On the other side, it's also teaching people that they shouldn't want to be in the upper class, because then they would lose this important sense of money.
As a hook for the article I thought it was clumsy and unnecessary.