I wonder if she at least clears closet space and recoups a little cash by selling her too-small but miraculously un-wrecked clothes on Ebay, or local buy-sell-trade sites. She buys so many fucking clothes, and a lot of it's cheap shit that would probably cost too much to return.
But she's exactly the type who would just throw away anything she's damaged, or is bored with, because if she doesn't want it or see a use for it, why would anybody else? She's that self-absorbed.
Since both her mother and sister were both obese and both died prematurely, Anna may, on some level, feel like she's doomed anyway, no matter what she does. Reversing her level of obesity and the toll it's already taken on her health is going to be a long, difficult process, full of sacrifices, and would require her to develop a level of self-discipline she doesn't already have. And there's no guarantee it would work; she could make a serious effort, lose 100, 200 or more pounds, and still die because her body's just too wrecked to save.
And if that's the case, rather than face those feelings, and at least try to take care of herself, she's just said, "Fuck it," and is determined to go out in an orgy of food, booze, new clothes, foreign vacations, and YouTube/SM attention. Maybe, by getting enough attention from internet strangers for her impulsive fatgirl antics, the world will actually notice when she inevitably dies, and miss her, and her life won't have been a complete waste.
Another thing about joint replacements: they have a limited lifespan. If you get a knee replaced, the artificial joint is only going to last 20-30 years, depending upon the stresses it's subjected to.
So if you know you will eventually need joint replacement, it's in your best interests to do everything you can to postpone the first surgery as long as possible, which includes losing weight.
It used to be that most people who got hip or knee replacements did so in their 60s or 70s, and died before they could outlive their new joints. Getting a knee replaced at 40 because you're obese and have wrecked it by being 100+ pounds heavier than you should means you'll have to undergo the same surgery again at around age 60--assuming a best-case scenario in which you don't end up with complications that require surgical revision.