Absolutely beautiful and sensitive.
Two spots where you might be picking up photographic distortion (besides your ditital white-balance issue):
- double check the size of the head in relation to the shoulders. Do this from life, if possible. It looks like your reference photo might have been taken with a shorter than 90mm focal length.
- check the reflected light next between the ear and cheek on the non-lit side. It might look that light in your photo reference, but as you have it, the value is the same as on the lit side of the face, which would not happen in nature under the lighting story the rest of the piece is telling.
- check the inside corners of the eyes; they don't match up and they should.
Gorgeous. Are you familiar with the pencil studies of Ronald N. Sherr? He employs a graphite wash that gives a very delicate, ethereal result.
I look forward to seeing more graphite work!