I Like how you captured her type...very cool. A few things to look at:
It feels like you added too much skull to the top of her head and not enuff to the back. ake a look at your reference again and double check those proportions. One thing that can be done, is to lower her hair line a bit. Right now her hair feels like it is sitting on top of the head rather than part of it.
Remember, the hair is meant to accentuate the roundness and planes of the form. Find that cylinder or box or oval of the head, that is what the air rests on.
If you could, I would post the photo reference so we can see wat you were looking at. Cause right now it feels like she was looking down, which changes a lotta proportions.