The proportions on the face are spot on. Immediately I am able to look at this drawing and recognize who it is. It was obvious to me that you had put in a lot of work into the eyes and it shows; those might be arguably the most important feature of any portrait since that is what we tend to focus on first.
The contrast between your light and shadow shapes were bit lost in portrait; I see defined darkest darks but not the brightest brights. This tended to take away from the contour of the figure and flatten her out just a bit.
All in all, I think you did a fantastic job and would like to see what you do next