I like the soft lighting here, but other than being a nice portrait it is a little uninteresting. It would be an even better portrait if her face was in focus and not her ponytail/bun thing on the back of her head.
You seem to have a common problem in all three photos you posted about. First off would be the lack of sharp focus. If you were going for a soft focus look, you need to start with a sharp image. By looking at your settings, you use a very small aperature when you could use a much larger and get faster shutter speeds giving sharp results. There is a lack of contrast/flat light. Last major problem would be the darkness around the faces. On this photo, fill flash would have made the subject pop much more while still maintaining your mood.
I like the lighting and the pose and the slight desat of colors. I would have given this a 6 as it is. If the face had been a little more in focus (it looks out of focus here rather than soft focus) I would have given it a 7. I think it meets the challenge.
Just read your post...thought I would leave a comment... I think that it's an interesting shot. She definitely has an intruiging look on her face. I think the reason it got voted lower is because her eyes are in the shadows, and her face is a bit out of focus. Hope this helps a bit. ~Magen
Her pose is an uncomfortable one, especially for such a tight crop. Her face which I assume is the main part of the subject is in the shadow. In other words the lighting balance dioesn't really work IMHO.
I like the desat and the mood you explain you're trying to impress on viewers I think comes through a bit though maybe a bit too subtle. Once thing that would probably improve the image is to increase the contrast. This would bring more attention to the face and the model's expression.