When too much of a young girl’s brain space is occupied by looks and you need to address that problem, you have to keep in mind that boys have nothing to do with it. It’s about perfectionism, like obsessing over straight As but worse.
Girls don’t care what boys think. They may think that they do, but if you’ll notice, being told that they’re good-looking holds no meaning for them—no matter who’s telling—if they’re determined to think that their physical traits are a problem. What they want is to like what they see when they look at themselves.
The problem isn’t that they judge themselves harshly. The problem is that they judge themselves, which wastes time that they could spend doing something useful or at least less destructive.