It doesn't matter what she did to lose the weight. The fact is that she lost the weight and she proved in capable of keeping it off. People like her are the ones who fail at every single diet again and again. She needs to address the underlying issues. You can't lose weight and eat like you used to do.
This is why Doctors frown upon fasting or any kind of diet where weight is lost quickly. If you lose weigh quickly you don't learn anything from it where as if you go to the gym and sweat the pounds of and control your portions you learn how to live a healthy lifestyle.