My High school sweetheart was considered the prettiest gal in school. All the guys envied me, she could be so loving, then she had a narcissistic Mother, that would shame her and torment her, it messed with her and to this day. Today, she's a bitter person who can't deal with the fact that she's no longer the beauty that she was in her youth, from what I heard, her heart had blackened and is no longer that shinning light that she used to be.
It often goes far deeper than the mother. Not all, but quite few girls of the type of girls you mention, spend more time washing their hair and doing their makeup than they do on their academic work. They attract plenty of guys, but their Daffy Duck like intelligence drives off most of them within a few weeks. This leaves them with the guys of similar intellect as a result of spending most of their time at the gym. When two people BOTH have ONLY a largely physical attraction, it rarely lasts. How many times have you seen media coverage of two celebrities in this situation having a showbiz wedding.? Then less than two years later their divorce makes the headlines.
I know a woman who was #5 academically in her high school class of over 400 kids. She was also a very pretty girl. She seemed to enjoy the fact that her looks got her more attention than her brains. She did go on in school, earned a Masters degree in her field - but now as an older woman, she is no longer pretty. She can't reconcile her looks now and sometimes tried to remind people how smart she is - but it is out of narcissism and a need to be recognized for her looks seems to overshadow everything. It isn't easy being beautiful, you know.