I would also add to the point
@JaneThough is making that there are certain physical/chemical differences between obese and healthy weight people (besides the fat and the limitations it causes) that both encourage weight gain and work against weight loss. Things like the bacterial biome in the gut can differ between healthy and obese people, and the brain's chemical reaction to food and how it processes hunger/full signals changes as you gain weight and keep it on. Furthermore, your body goes through certain set points of weight, weights at which you might hover for a while before seeing significant change. The problem is, you stay at those weights for long enough and your body begins it recognise it as its new 'normal', and the brain's chemical reaction in deciphering whether it needs more/less food begins to defend this new point as the weight it should be, even when that weight is too heavy (which adds to the already confused system of overly-processed food tricking the body into thinking it's taking in less fuel than it is because of the lack of nutrients, while actually consuming high numbers of calories). A person who does not have a weight problem, but then temporarily gains weight for some reason and loses it, will have a completely different reaction to food at the chemical level than someone who has been obese/morbidly obese long term as there body will still recognise their lower weight as the 'right' one. It makes those comparisons of 'I did it, so can this fatty' less equal than things would suggest on the surface.
It's also the reason weight loss surgery has a far more effective success rate than diet and exercise alone, because the process of going through the surgery (the limited food intake for the pre-op diet and the post-op period when you genuinely can't eat much food for quite a long time) helps to resent both your gut biome content and your brain's understanding of what you need. The actual, mechanical restriction will get looser with time and is the least of what the surgery helps you do. Obviously nothing is foolproof and if you don't change your habits you can still fail, but it helps you get out of your own way physically speaking (mentally/food relationships being a completely different animal).
Sorry, that got super long and I don't know how to do one of those cut/spoiler things to shorten it, but legitimately, losing weight as a long term obese person is a completely different experience, so her take as a morbidly obese person who has lost significant weight is way more relevant.