Oh thanks everybody! These comments certainly were useful.
@Mike
Thanks for the animation! Although I think it is kind of exagerated as I would prefer a breathing animation to show her concentration instead a fighting instance, the movement you made is a nice reference (:
@tehwexxl0rz
I think androgenous is OK, as I believe there will a be short cutscene showing no helmet on her. But I do agree the shoulders are wider than they could be. I'm sticking to the helmet, though. This big is adding a lot to her silhouette and meaning there is actually a human head inside it - the smaller one you did seems like a "pure" robot head. I did borrow some of the adjusts you made on hips and shoulders, thanks a lot!
@StarRaven
Thanks for taking time and answering. I asked some people about the other colors. As the character will be anything but kind, blue didn't quite well (and it seemed like a police armor), and although red is excellent for some main characters, well, there are too many of them and almost none is white. Pinkish and purpleish armor seems kind of "evil" too, this is not what I wat for her - even though she's not good, she's not an asshole too haha
@Helm
Many thanks for your advice! I didn't really understand the color banding problem, but I got what you meant for the shapes, specially the helmet. You're right about the thighs too. Even though I didn't shape them as you did, the lower part of them, where it gets near the knee, were poorly shaded. Borrowed some of your pallete too, hope there is no problem about that.
Well, finally, the new sprite:

Still don't know which one is better. What Erekt said about keeping one color for armor and another for "cloth" is efficient , I really like the idea of the dark part of the helmet seems like a big visor. However, while it's entirely white, it pops out enough to say "hey, I'm a white character, you know?".
About comments: I do agree with Helm, still, although I was pretty confident about my skills, I was not sure if the final result was effective, anything would do. Not simple encouragement, but comments like Seiseki's. He pointed the right things and why he thought they were right. I needed different opinions and Pixelation showed me a long time ago that there are plenty of artists with different skills and opinions to add to your work. I was quite participative and helped others, but when I needed help again, I got no response at all.
Anyway, maybe there are too many variables for why this happens, don't know if it is really productive to keep this discussion here.