Food and exercise are 2 completely different things though.
You say you cannot believe food alone can make you balloon that quickly but did you see the size portions she was scoffing? She halved everything which meant she was eating the same sized meals as Boring Bean! And that's just the stuff they showed us, never mind what they were eating off camera!
Exercise has been proven to keep you healthy, no doubt about that, but as the saying goes, you cannot out run a bad diet, in other words, no matter how much exercise you do, if you over consume, you will not lose weight. Surprisingly you can lose weight without any exercise at all. Exercise is great for overall health, including mental health but its a small contribution to weight loss in the grand scheme of things, its what you eat (or don't eat!!) that gives you weight loss results.
Sure, she could do with generally moving more, coming home after a couple of hours work and sleeping is not normal for a young women!