It could easily be close to true and she's just fucking stupid.  If she's short and had a tall, skinny boyfriend (which is not that uncommon to see) he could easily have twice her BMR.  So if she's an idiot (and she's fat, so she is) then she probably doesn't count her two 700 calorie frappucinos a day, meaning that even though she's eating not as much as he is, she's still taking in way too many calories.  In short, sufficiently advanced stupidity is indistinguishable from lying.