Whoah, amazing.

I love the back lighting, it's my favorite lighting in art and photography! The white outlines make the subject jump out from the background every time.

The expression is ok, but she could smile a little more with her cheeks a little higher.

I like how her mane looks like the starry sky. I would make the mane a lot longer though, I think it would make er look more... epic.

The eye reflections are very nice, coloring - awesome.

Great work, keep it up :3