"Gamine: a French word, the feminine form of gamin, originally meaning urchin, waif or playful, naughty child. In the 20th century, came to be applied in its more modern sense of a slim, often boyish, wide-eyed young woman who is, or is perceived to be, mischievous, teasing or sexually appealing."
The short hair is mandatory, in my mind, to achieve this feeling of boyishness, but only works in combination with features highly dictated by estrogen markers (anime eyes, nose and mouth). Short hair alone, say, on a more sophisticated beauty like Isabella Rossalini or the lustier features of Angelina Jolie, do not a gamine make.
This hyper-feminine face is not in need of hair or make-up to prevent it's being confused with a young boy's, yet there is no mistaking it for that of a woman's - first and foremost the gamine requires fresh-faced youth.