I love this. The way the light plays across the shadows and contours of her body combined with the red and black angles gives this piece a very stark and severe feeling, but there is a softness to it also. I love the tiniest bit of blue/grey that is visible in your models eye, it adds a bit of power and a confrontational look to her face. I think you did a lovely job.
Just shut up about the model please and enjoy the piece of art. I'm so sick of women saying "oh, that model looks so skinny it's unhealthy". Unless you're a doctor and have her as a patient, I don't think you have any idea if she's a healthy person or not. No one wants to hear your jealousy.
It's entirely possible that she is naturally thin, some people are, but either way her health is not really what this is about. If you wouldn't tell a slightly overweight model she looks unhealthy, perhaps save us naturally slender girls from the criticism as well.