A gamine is a slim, often boyish, elegant young woman who is, or is perceived to be, mischievous or teasing.
Audrey Hepburn has been cited as the epitome of a gamine.
A waif is a person removed, by hardship, loss or other helpless circumstance, from their original surroundings. The most common usage of the word is to designate a homeless, forsaken or orphaned child, or someone whose appearance is evocative of the same.
A young waif steals a pair of boots