Take it from a previous size 20 (UK size) serial dieter who is now a size 10! I lost 6 stone (around 35kgs) in 2 hard years of healthy eating and excercise after years upon years of trying all the teas/ pills/ fad diets out there
I know its cliche but it works if you're willing to put the hard work into it. I've been a size 10 maintained now for 2 years and it is hard work - ide prefer to sit in and eat pizza than have a salad and go to the gym. But yea, she needs to be careful as it gets to be an obsession. How old is she and how much does she think she is over weight if you mind my asking?