The former Ms. Middleton still wears denim, at the appropriate occassion. You can, if your filter allows, find such pictures online.
In Brazil, appropriate attire is interpreted differently than in England, for men and women. Cultural norms certainly do play a role, that much is clear from halacha. These “how to” books such as Rav Falks do not take that into consideration, nor can they, as they offer a one size fits all approach.