To make the face more feminine, the jaw needs to be smoother and the brows less emphasized. Fuller lips help, but are not necessary.
I think the face needs better structure overall. There's no real anatomy here, just an egg shape with parts in roughly the right spot. Eyes should sit in sockets, nose protrudes, and so forth. I see that you've added shading to emphasize form to the other sprites, you just need to do that with the face too.
The hair looks plastic and doesn't sit right. Unless she sings for a Flock of Seagulls
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The face needs a highlight color. Noses usually catch a highlight and the cheeks sometimes too. Stronger contrast between your existing shades would help too.
Quick edit using your colors. You've got about 40 pixels here, use them!
1) Same face with a generic smooth jawline. Changed the eye shape and added eye sockets. Tweaked the nose, gave her some lips.
The eyes are already a strong contrast with the bright orange color. They will show up even when reduced in size.
Instead of combining the eyebrow and upper eyelid, I separated them since there is plenty of room on the face.
Gave her a quick haircut. The hair still needs a lot more work, but at least you can see her face.
2) Same as above, turned the jaw slightly to one side and made it stronger. A stronger jaw is good for athletic or amazon characters, but it can be masculine if you make it too strong.
3) Same as above, but with a narrow jaw. I think I overdid the hollow cheeks, but this one looks thinner in case the character is supposed to be a model or something similar. A difference of only a few pixels. (img 2 vs img 3).
The edits are a bit generic, but I hope they point you in a better direction. She still needs highlights on the nose, and light and shadow to define the shape of the cheek. Your choices there help make the face distinct.
Hope this helps,
Tourist