Letizia ,Maxima and Mary was all married after their 32years to crown princes,Lala salma is the lonely woman who was married to a King and she was only 24,it makes huge difference,we don't know how would behave those royals if they were at her age,also an example,we all know the huge difference of Mett Marit at her 20's and what she's now.
Personally,I think that Salma's beauty is not very common,and she have something different which shines on her appearence,I ve also heared that people who approched her said that she's much more beautiful than in pictures,inlike QR of Jordan who is said not half pretty how she looks on pictures than when seen in person,so it's also a question of being photogenic.One thing which is sure,Salma is has a natural beauty and she's extremly a nice and warm person.
Also,I don't agree when it's said here that her hair is old fashionated,not all people can wear curly hair,iom it's a very modern and unusual hair style for a royal woman, she has a very nice redhair color with beautiful natural curls,maybe she have only to change the hair style time to time,and not to keep always the same style.