A sylph is a lovely, slim young woman or girl. You could describe a row of graceful ballerinas as sylphs.
A sylph is always young, female, and slender, moving with an almost otherworldly lightness and grace. The original meaning of sylph was a mythical fairy-like creature, an air spirit that's mentioned by the poet Alexander Pope and appears in several Shakespeare plays as well. The 19th century French ballet "La Sylphide" is thought to have led to the use of sylph to describe slender girls, especially ballet dancers.