This is a great capture. I love her expression and the lighting/selective desat. The focus on her face seems a touch soft (even though the hair SHOULDBE the focus for this challenge), still like a sharper face
Terrific portrait and smile. I would love to see this "cropped" a little closer in (in camera or editing) and ideally, without the shadow crossing her face.
Not sure what you want us to see as the defining feature of your very attractive model. Her hair is looks as if it might be that feature, but then why has the whole girl, rather than any one of her features (such as her hair) been made to stand out by having the background desaturated? I like the image, but I'm a bit puzzled by it