In my opinion, the subtle simplicity of the face was lost when you painted it. I dont think you need to show the cheeks rounded towards the middle of the faceit squishes the face. And in doing that she lost her slight smile; which now doesnt go with her come-hither eyes (that confident sleepy-eyed look).
Keep in mind that this is not a personal attack. It is my unsophisticated opinion, but I liked your sketches better. In fact, I liked the fear-of-God look better than the come-hither look because it is more in line with being called upon by a deity from another realm
unless she is the REAL master. But then why is she walking off the cliff?
Im not suggesting you conform to my ideas about what looks better, but in my opinion if certain elements in the composition are in conflict then the viewer is going to notice it right away as unnatural. Now its hard to pull off something unnatural unless you are going for a more modern art/abstract kind of elemental-conflict thing. But I think you want the viewer to have a clear understanding of whats going on in the picture.
I dont have any great advice for your use of colors as I am a horrible painter but I will say that the color looks flat. Subtle color changes through tints, tones, and shadows will bring out depth.
I have good things to say too. The good things are that this is a great concept and you draw well. Perspective is great and you work quickly. I am not disappointed in your entry but encouraged by it. CGTalk is the place to get great advice and you can only get better from here. Good luck my friend.