Of course there are genetic influences on ease of gaining/loosing weight and how a person looks. But it's also obvious that a huge share of obesity is related to modern living conditions and the choices that people make. If it were true that genetics predestined most people to a certain weight, then we wouldn't see the humongous rises in obesity that come about with industrialised food production and sedentary Western lifestyles.
It really doesn't take "several hours a day" or "6 days a week" for the average person. Most people are amazed at how much weight they lose when they just cut out things like soda and packaged foods from their diet, and if you add some light cardio (or even just getting up and walking for a bit) every day and maybe weight training for 30 minutes three times a week, it's enough for most to remain fit and healthy.
Do people have to do these things? No, but it is an excuse if they forgo them while claiming that how they look must be genetic. That weakness of character is broadcasted to other people, and it can't be wished away as misogyny or the promotion of anorexia.
It's not about the fact that women don't look like her. It's about the fact that people in general want to do the least effort, while expecting others to believe them when they say they did the best they could. People do make excuses, and it's incredibly sad to see them do it. They say: "this is just how things worked out, and there's nothing I could have done to change it". It's the same whether it's a woman who resigns herself to weight after pregnancy, or a person born into poverty who resigns themselves to being poor all their life. The most respectful thing that can be done for them is to not accept their bullshit that they're completely powerless and without agency.