Aah, I wish I had your skills~ I'm so jelly. seriously. >< How you managed to shade so perfectly is unfathomable to me! The lines are so gentle and sweet, and the colors used contrast the picture even more precise and neat (i especially love the rippling water below). My only suggestion, as said by shiilus below, is that the facial anatomy does seem a bit disproportional as I feel as if the face seems a bit too high up.
This piece is very pretty, I love the shading Martinique and the colours used. The way the have coloured and created her clothes makes it actually look like a sort of water pattern too! They way you have spread out the stars looks so lovely and even and the ripples in the water give it this extra lovely effect!
However what I have to say I dislike about it unfortunately is the facial anatomy. Everything seems to pretty and perfect, but the facial features seem a little too high up the face. It gives her a really large and dominate chin which takes away from the cuteness! If you tried moving everything down a little or making the face shorter it would work about a lot better!
Now, I hope you don't mind I've done this and I'll remove it after you have seen it if you wish! But here is an example of what I mean: [link]
In my opinion it looks a lot better! I would have also moved the eyes down but I'm not actually that amazing with photoshop ;^;
I've also pointed out some things there! Hopefully my handwriting isn't too horrid! But it says to make the crown slightly larger and slightly more to the centre of the head, and move the eyes down just a tad to be more in sync with the nose and mouth! Also maybe make the neck really, really slightly less long and also it would help to shade the nose more so it looks more prominent! At close view it only looks like it has one small little shine to it!