I guess I would use the reference of the pupil to pupil line, as it looks like you've got it pretty much right on.
In your painting it seems the right upper eye lid looks a bit thick. And the line of the lower lid on that eye is a bit different than the photo. The nose may not be slanted enough. The break in the line of the lips is more exaggerated. Her left eye is a bit rounder than the photo.
Ok, I'll put my microscope away now.
