I don't know how both surgeries work. A friend of mine did have the one where they put a tube around the upper stomach to create a stricture so she can't eat a lot of food. It has worked, she went from 330 to 210lbs at 5'.11". Unfortunately now she has developed some severe acid reflux and needs to have her gallbladder removed. BUT, I do think that one is reversible.
This poor kid seems to be an all or nothing kind of person. If she eats, she eats everything, if she doesn't eat, she won't eat at all.