She had some help building up her couture collection from her good friends. The late and great Alexander McQueen was a close friend of Daphne's and she was often dressed in his whimsical pieces from his name sake label. Another good friend was Socialite Isabella Blow. When she died, Daphne stopped the planned auction of Isabella's wardrobe by buying the whole lot.
Even though Daphne had some input from her friends, Her style was all credit to her. Always dressed impeccable and a walking piece of art, Daphne definitely does not have 'casual' in her vocabulary.