Beautiful photograph of a beautiful (and very natural) model. I think the lighting is good, the detail is adequate, and her hair is great. I agree with the other commenter, however, that perhaps the cropping is the least interesting part of this picture. If you turned the cropping horizontally, it wouldn't seem so claustrophobic. There is something about the cropping in addition to her head tilt that make it seem like she's in a box. :)
The only other thing I would do is bump the contrast, only because there should be a better balance of darks and lights in a portrait, and this is more and the dark side that anything.
framing of the head is alittle odd, but i can live with it, the hair here is very pretty and i wish the it was a horz. orientation and the face was far left only half showing and the hair taking up the rest of the frame....inother words, great lighting and start but a different framing is required here...IMO, Good luck