Vanille is a character whose face structure is, in my opinion, very hard to capture. You, however, have done a stunning job capturing the emotions that she displays in the game. I absolutely adore the way your eyes seem to POP in this picture, as it creates a place for the eye to go after exploring the rest of the image. The necklaces add some color and variation, and the way they criss-cross over one another makes for a very strong picture in that respect.
It would be nice to have more focus on the hair, as it seems the top part is a little fuzzy/out of focus. The house in the background is also a little distracting, but fortunately it is within the same general color range of her hair. There is a "rule" in photography called the Rule of Thirds, which basically states that a strong picture is often made by not positioning the subject dead center-- this picture excels at that.It helps leave room for the eye to take in the entire image.
Overall, a very well-made cosplay (with the correct color wig, I might add, which is awesome ) and a photograph that has a rather strong composition. Good job!