This is my favorite of the challenge! 10
The selective Desaturation is so perfect to bring out the topic feature. A beautiful and tangible person. The Crop, angle and natural pose are all strong additions to making this a winner.
Great expression! I'd like to see more of this model. The lighting is interesting but the hair on the left side of the frame is a touch too dark, especially relative to the hair on the right edge, on the other side of her face. Also, there is a slightly distracting reflection on her forehead right at the edge of the frame. Like I said, the light is interesting but, probably as a result of the dramatic angle and hardness of the lighting, and also the B&W conversion process, perhaps more skin imperfections are showing? I certainly couldn't say without seeing a color version and/or seeing her in person, but just a suggestion. Softer, more diffused light would hide pores and other textural features of the skin. Playing with the channel mixer can either amplify or hide things like freckles and other color-related features of the skin.
Anyway, I still like the dramatic look of this photo and the detailed textures here. It's really different than a lot of the portraits you see of females.