Alina Buryachenko is one fine lady, maybe a bit too thin though. There is a fine line between being sexy "lean" skinny, to "anorexic" skinny. Being able to count all her ribs when she twists her body just a tad bit is almost anorexic to me. That is not a turn on.
Personally this pic below is my definition of "sexy" skinny:
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I think the correct word for it is "svelte". I love girls with this type of body shape.