Hey Ivan, I've got a few crits and an edit for you.
- Loosen her up a bit. Right now she is rife with perfectly vertical lines, making her look stiff and wooden. Try and avoid vertical (or horizontal) lines for organic things like people, instead use curves and bends to liven it up.
- On small sprites like this, the face alone can only be so feminine, and is usually mostly androgynous. You must use the body, hair, colors, and decorations to indicate the femaleness.
- Try and avoid "pixel noise". That is, pixels that are usually by themselves or in small groups that don't really communicate any specific thing. This is apparent on her shirt mostly, but the sprite overall looks a bit noisy and confusing.
- I like the hair! It's a good style and it reads well. I threw in a few highlights.
- Be careful using such dark lines for things like the mouth. The mouth is a complex shape and to have a big dark line in place of it will brutalize it. Best to use a lighter color or two and thus leave it up to the viewers imagination to see it correctly.
- Working on a non-white background is a helpful trick. I like mid-saturated greens or blues.
Anyway, on with the edit: