Here's a little edit:
(I guess dithering can be applied in this case)
Firstly, I've made a few anatomical adjustments, such as shortening the torso, shortening & unbending the arm (you'll have to excuse the feet I made, they are terrible). I didn't put in any outlines, I don't think they're needed at all. Notice how the side of her head which is turned away from us is in darkness as dictated by the lightsource. I've used a lot of antialiasing especially on the head and, this way, more detail is emulated. I messed around with the colours too, bringing the count down to 16. Hope that helps.