People who have psychological problems. Believing in HAES is just rationalizing their using food as some form of comfort. Like any drug abuse or addiction, people use it to escape from something else.  There are people who've internalized bad eating habits and have an extreme or skewed lack of knowledge about nutrition which were forced upon them as children, such as the parents giving the kid soda, juice, other sugary drinks and junk food all the time. You'd have to see where the root of her eating too much stems from and what's stopping her from lowering her calorie intake.