This is such a powerful piece. She looks very said but also like she is contemplating something. The realism is dead on and absolutely stunningly gorgeous. I like how you can see the textures in the face. Her eyes are very lovely as well. For a sad piece the hair seems a bit wild so it sort of contradicts it a bit, but the hair does look very real and fantastic. Your background is simple and blends in with her clothing so it does not take away from her one bit.
This is amazing, you did a great job, keep it up~!