That's really a special moment of expression on a face - s bit strange, a bit soft, a bit suggestive - quite an intriguing mixture. The soft focus reminds me of pictures and movies starting back at the 1920's (or perhaps even earlier) when "the girl" was most of the time captured this way that avoid hard contrasts and sharp contours. If you saw the one and only Ingrid Bergman in some similar portrait take of a movie you will know what I mean.
But then again, the white background seems to be a bit too much as it somehow "competes" with the softness of the face. Perhaps getting it closer could put the softness of the face in the absolute center of interest on this composition? (See also cropped attachment.) I am not very sure about that, though, since the white wall does play also a role by adding some elements of high key photography that complement the softness of the face well.
So, staying in your composition, the only thing that I find not very good is the additional hair at the left of the face that makes the cut of the top of the head "harder" that it really is. If it weren't on the image that cut wouldn't be very noticeable.
A very nice portrait all in all, that also makes me ask you if you directed the girl to pose, or if you just let her do what she want and shot when the moment was right.
0 
{K:127263} 3/4/2007
