The tiara looks nice and twee, just right for an 18 year old princess. It's just that the 18 year old princess looks like a 38 year old princess.
Just compare her looks, charisma and behaviour to that of some other 18 year old princesses like Ingrid Alexandra
I have to add that it is also culturally driven. The 'south if Europe (more specifically Italy)' glitter glamour ostentatious Gianni Versace ott, the ' north of Europe' wholesome, normal, humble, authentic.
Even apparel companies work along these lines- selling the same model clothes in a completely different palette of colours.