This is a good attempt David. Unfortunately the photos don't do the piece justice. I use a camera from my phone like we all do these days and the results don't do the models any favours. From the image I see I would try to "round" the iris of the eyes just a little more. Her left eye seems to be the problem. From the photo it appears that the left iris is a little straight edged and coming to a slight point towards the outside of the eye. You have got the eye positioning perfect but they need to be a little more round to get that stare. As I say it may be the camera. Also I would use a dull coat varnish to take the shine out of the clothing. Girls are not easy to paint and especially this girl as this photo is so iconic, but you've done really well.
John