First of all I really love the way you did the colors with her. Most usually go vector when using colors like you did but the sketch lines adds a little history to her. Shading covers the right areas, especially on the tail which I can imagine is tricky to do. The wings look more like fur over feathers that Alicorn/Pegasi have though it is unique if you did it that way. The tail appears a little too ragged but brings up the idea as if she were hiding from something or someone.
Overall I believe you did a good job with her design, is original and if she has a back-story it would be awesome to see.