Actually plastic surgery probably would not help in the situation of someone believing they are ugly.
Maxwell Maltz, a successful plastic surgeon, wrote a book: PsychoCybernetics, about how people with deep seeded personal images of ugliness in many instances still find their person to be ugly even after undergoing dramatic plastic surgery.
It’s a psychological disorder and prevents the person from actually seeing the change as beneficial. What he basically concludes if you feel ugly, no amount of surgery is going to make you stop feeling ugly. Only deep psychological change in ones self will heal the person from believing they are not ugly.