You mentioned that the only issues with her was that her arm was as big as her waist. I can assure you, it was deliberate. Along with some mild perspective, she's emaciated and has no waist at all, really. I wanted her to look unhealthy and a little creepy.
And, honestly, I can't really help you out with technique, My drawing and coloring style are extremely random, and I doubt even watching me would be of any help... n__n;