fashion plate

Translations
законодатель (мод)
She's such a fashion plate, always dressed in the latest trends.
Она такая законодательница мод, всегда одета по последним тенденциям.
Definitions
A 'fashion plate' is a person who dresses in the latest styles and is considered to be very fashionable, often serving as a model of current trends. The term originally referred to illustrations or engravings showing fashionable clothing, but now commonly describes someone who is notably stylish.