The eyes are beautiful, especially with the color; blue, green and the monochromes. The skin folds below the left eye are shaded and blended well, but the one one below the right eye isn't blended that much. Looking from a distance, however, this isn't a problem. The negative shading for hair is done very nicely. Some parts of the hair could have been darker to create more contrast; however, as I have not seen the reference image, I am inclined to believe that the reference dictated such shading. The background color complements the eye.
Everything else looks great. You have worked meticulously and it shows. Usually, I do quick sketches and light shading, but I have worked on one or two portraits (never uploaded them here) and I know how difficult it can be ( especially, in my case, without a fine/retractable eraser). A little more blending on the forehead and some other areas might give better texture to the skin. Overall, this is a very promising work.