A gamine by modern definition is a wide-eyed, elegant young woman with mischievous or boyish charm. The word gamine is of French origin. It used to mean street urchin. Street urchin! I'm not sure how the word traveled so far in its meaning. The modern definition is far more appealing, don't you think?
The modern definition also suits imagery associated with gamine style. Gamine style is youthful, classic, often simple, a bit tomboyish, and a bit ladylike. The young woman below captures it well.