With pixel art that uses models, part of the challenge tends to be not to be as accurate as possible, but to deviate in the ways that best brings out the overall qualities of the image.
E.g. in this case I'd argue that the big flaw in the end result was to not bring out the blue in her head-dress and the white and black in her eyes, and ensuring the back of her head and back is actually visible, at least with a dark grey outline, as well as the red line of her mouth.
Likewise, sacrificing some of the lines in her headdress for less texturing but hinting at it with maybe one line would probably look better.
I don't want to diminish it in terms of demonstration of the methods in the article - it's great as a means of showing what you can do with them. But it also demonstrates shortcomings of those methods (but that's good too).
Here's a portrait of R2D2: https://www.flickr.com/photos/152507766@N07/32877646570/
and here's the Millenium Falcon: https://www.flickr.com/photos/legocityson/37717492631/in/dat...
and Groucho Marx: https://www.flickr.com/photos/125619484@N02/29571498821
and a self-portrait (not me): https://www.flickr.com/photos/142720019@N08/33587002231/in/d...
[1] https://www.youtube.com/watch?v=k9ENEj33t4M construction video