I really like the details here; the shading, the separate strands in the mane and tail, the expression and the eyes, and the pose that really lends for a sense of energy. Cool stuff!
It looks so clean somehow with the soft way that the hair bends in. And the proportions are very accurate. Except for the ear, isn't it a bit to small?
I think it's her eyes, as well as the hair color and style accentuating the eyes.
That, and she's just pretty cute.