This looks pretty good. I just had one question, is there a light being shone into her eye? The iris, left─from her perspective─side of her eye, and eye-lashes are considerably brighter than the rest of the piece.
Just noticed there seem to be some purple specks on the left-side of her face directly beside the eye. Odd. I had no idea ponies had freckles.
Saved into the exponentially growing pile of potential cover-art─with credit and source, of course─... Great work on this.