While the overall structure of the girl is solid, the shading doesn't reinforce the structure. When in doubt, I prefer to simplify or eliminate a line for clarity, and emphasize it's shape using lights and shadows. You've done a good job of communicating form without using a jumble of lines to show detail, but the shadows and highlights don't compliment the line art as well as they could. I made a small edit and will explain the changes in the hope you or others will find it helpful.
HairYours is looking very pillowy, and it has white pixels next to very dark pixels, which makes the hair look jagged in places. Also, the flow of the hair gets lost towards the back of her head. I went for a simpler more cyber punk look. I tried to make it clear that her hair is tied back on the far side, and it's spiked out on the near side.
FaceI made it clear that one side is getting hit by a rim light and that the other side is in shadow. I like the dramatic effect, so I also threw in dark pixels next to the rim light to make the effect stand out more. The nose and head also cast drop shadows, adding to the drama.
BustHaving armor that changes from smooth curves to sharp angles is tricky. I took the easy way out on the shoulder armor by making it completely angular. The chest piece took more work, and I found it more efficient to use highlights and shadows to describe the transitions than relying on lines.
SwordSomething I learned while working on the challenge was that 45 degree angles are your fried in you aren't going to rely on AA. And they are great especially on mechanical objects like weapons. I also learned that while you can get away with odd angles on larger objects, such as the cube your girl is sitting on, smaller objects, like her sword, turn out much easier if you keep the angles straight.
I would suggest you work to be more bold and structured in your shading. If something is supposed to be in shadow, make it clear that it's in shadow. Don't thow a bunch of shades between every light and dark, or you'll just end up pillowing the piece to death. It will make your work much more readable as a whole.
