I'm not sure how much weight the fluid would add, but I'm down to 311 pounds now, and I still have trouble getting the armrests down since I carry most of my weight in my butt. :blush: My hips extend about 1" into the seat next to me, so I still have to purchase two seats (which I don't mind, since it means I'm more comfortable too). I can fit in the standard seatbelt now, but when I was 360 pounds, I had to ask the FA for a seat belt extender. Anyway, even if she put on 100 pounds of fluid retention, she still would have been too heavy at her "normal" weight.
Whatever the reasons, it's sad this lady died, but at the same time, the airline has to ensure the safety and comfort of all of the passengers. The mandate that heavier passengers need to purchase an additional seat if there isn't an empty seat next to them isn't a new thing. Most airlines have it under their passenger rules on their website now, and the gate agents have been trained in tactfully explaining the rule to those who might not fit (not that it's often enforced tactfully, but they do try).
Interestingly enough, in Canada, an obese person is not required to purchase a second seat under the disability laws. In America, it is not considered a disability (nor should it be). I got heavy because I have insulin resistance and wouldn't keep carbs and sugar out of my mouth, causing me to gain weight rapidly. Now that I know better and don't want to die when I'm 40 or continue to be embarrassed in public, I've knocked that nonsense off and the weight is coming off. I don't make excuses. I screwed up, and now I'm doing my best to fix it. If someone is gaining weight for a truly mysterious reason, then they need to see their doctor. If I'd done that years ago, I could have prevented this huge gain, but I was in denial and used to be one of the whiners who wouldn't take personal responsibility. :unsure: Stories like this are sad, and I'm sympathetic, but rules are rules.