Good start. I see anatomy problems but I'm not the most qualified about it, let's see what others say.
The pose looks impossible to me (try it in the mirror): with the weapon shaft behind her back, her right arm should be thrust back or her forearm turned to be almost parallel to the shaft.
The left arm (hers) is too long (would reach down to her knees) and evenly thick near the elbow.
Her right foot either doesn't touch ground and the rest of the body doesn't support this, or the point of view is from strictly ground level which contradicts the overall aspect. In other words, lower that foot by ~1px.
The pose is more of a parade or dance than a fight. No prob with this, just wanted to make sure that was your intention.
From a composition p.o.v., the large blade takes too much space / attention.
Beware of
banding in the shaft.
when is it okay to sacrifice anatomy detail for something to look 'pretty'
Pixel art is all about sacrificing detail to readability and efficiency. If 'pretty' is geared toward these, you should be fine =)