That's a nice reference pic -- lots of shadows to describe the shape of her face. It will make a nice drawing.
I put your images into GIMP, scaled the drawing so the height of the heads were equal, put them in two layers of the same image, made the sketch semi-transparent, increased the contrast, and moved them so that the faces lined up. As you can see, the mouth and nose are in the correct positions relative to the head size, but the eyes are not at all. Also the forehead is too high, and the placement of the jaw is off. The angles of the eyes and eyebrows are off, too.
Hope this helps -- sorry it sounds so critical.
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