Here's critique.
You do not gain from having worked from a high resolution cg image because it does not help you think like a pixel artist.
At this resolution, how powerful is a single-pixel fat line? The black lines outside overpower the soft sading inside (squint your eyes) and they invalidate it. It's like it doesn't exist. The pixel clusters are merging into a big blob of yellow.
The problem is further exacerbated by that, due to following the cg image you have created a lot of 'connection points' where the outlines of various forms on different planes converge on the same spot, and flatten the image. Look where the left wing touches the hair and the other wing. Look where the long hair touches the legs. What is in front? What is in the back?
You're not shading as if your forms is made of pixels. You're shading as if the pixels and the forms are separate things. You have in your mind visualized the forms from the cg and are resisting in using your colors to make the whole thing MERGE into something made of pixels, pixel art. The contrast is borrowed from the reference and as such doesn't work. You are lacking darker range because the reference is done like comic art. Black lines and a light middle shade for the body, more or less. This won't work for pixel art of this size, of this subject matter, of this aesthetic. You'll have to sculpt it with a full range of color. For instance think of the back leg, why is it almost the same value as the fore leg? Shouldn't they be separated with shading so the player knows what they're looking at?
A big part of the problem I see here is that from checking the png I see you're not actually working much like a pixel artist. You have shades that are underused in just a few pixels, you have a broken alpha mask that you simply don't need for something made of 16 colors like this. Your methods are obstructing you from becoming a pixel artist. What is your goal from using pixels to do this sprite? You need to switch mindsets if you really want to use pixels for these small sprites.
This image is extremely challenging to properly shade without arriving at selout hell because of that there are so many curves to convey in such a space where a single pixel row worth of difference is too steep a move. It takes masterful skill to get it to work both on black and white backgrounds without using black outlines or selout. Selout is not my taste, but why didn't I use black outlines, you might ask? Because your image in not made from outlines and fill-ins, it's made of PIXEL CLUSTERS and they need to be addressed as such. Pieces of shading conveying volumes under light, outlines only diminish the womanly form here.
Simplify the wings, even go with pure black if you like (though I like the ambient blue personally), the more they merge with the hair, the worse for the piece.
Shade as if you're doing pixel art. I can't explain this any further. It's different from when you're shading something with pixels that in your mind is still a CG image. Avoid the banding issues you have, work on your curves as much as possible.
edit: also wanted to mention that at this size the reference image betrays you and it mostly looks like she's an amputee, better have the arm extended I'd say. In the bigger CG version it could work, here, more clarity is needed.
