I like your character design! Centaurs and other mythological creatures are a favourite of mine.
The shading at the top of the hair is really nice and blends well, but the shading on the tail doesn't match up to it, and it looks more like a line of grey than shiny fibers. The shading on the rest of the body is fine, but the girl's shirt could also use a bit more dark tones.
Your anatomy us good for the most part, but her left arm looks like it's bent the wrong way, and is backwards. Try having the elbow turned a little, so that her hand is pushed more to the front. The position it's currently in seems kindof uncomfortable. Sorry, I'm not very good at describing how you should make it, but a tip that always helped me was to stand infront of a mirror, and bend your arm the way you want it to look. Also, the muscles on her chest look like they're offcentered a bit.
Overall you did good, but there is always room for improvement, but don't worry! You can do anything if you try! ^^
Ooh a centaur! Great creatures. I like how you let the light shine in her hair. Well done! also it can be quite hard to draw a horses body but you did great. It's good how you made the body more dynamic by bending the front 'leg'.