but what can I do? I don't know, maybe I make her wearing a leather biker cap?
What you can and should do is not run away from the challenge.
I second that!!! in fact i was about to say it, damn you Helm!
a very quick dirty.

make the hairline look more natural and the division between the shaved and 'haired' area of the head will look more appropriate.*
You lost a great sense of volume when you texturerd the hair, when texturing it is important not to lose sight of the big picture. What you had made it nearly look like her brains were showing.
Yeah just a repeat on the neck lighting comments.*
Also something about the area above her left (on our right) eye seemed a little puffy, not sure if i fixed it, wasn't a big deal.
For some reason I felt a need to accentuate the face jewlery. I think they might stand out a little more due to metals high contrast. But what you had isn't really that off.
*: Careful with strong solid lines in creating faces with pixel art. Because of the grid like nature of the medium it is very easy to over do it. I see that you are wanting to create a fairly powerful look (this is particularly evident with the nose) and by all means stark divisions of areas is the way to go, however the combination of this and pixel the pixel art medium can make you over compensate for what should come fairly naturally.
Good stuff so far, very, very cool looking. Also she reminds me a little of Jennifer Morrison from house for some reason.