This is a very interesting character. I like how you added the random objects floating around to show the kinds of abilities she has.
Your style is nice, too. The lineart is clean and crisp.

The main thing that may need some work is the values. There is a low contrast between the base color and the shadows. The lighting that you implied in the background makes me feel like there should be some darker shadows. You may also want to play around with shadows; try adding in a hint of dark blue to the shadows or maybe dark red (it all depends on your light source).
There are also areas where you'd want a crisp shadow, namely, the cast-shadows. Underneath the necklace is an example of where there'd be a crisp shadow.

Maybe it's nit-picky, but the fuzziness of the hair bothers me. You have a crisp lineart, but then suddenly stops at the hair and it's all fuzzy, unlike the rest of the outline. Maybe try making a lineart around the hair (like in a cartoon style) or make the hair composed of long brush strokes that make up the lock of hair and include little extra strands hanging around, as hair has a tendency to do that.

So, as a concept, you have a very neat character that is simple in design and yet very unique, but little technical things take away from the drawing itself.

(That little mouse is just adorable, btw! :3 )