Ahhh I think I see what it is - the eyes are roughly in proportion, but it's the iris' and pupils that are too big - you need to show more white there. Her ears are slightly off skew too - the RHS one is much higher than in the reference photo. I would definitely recommend trend lines for your next picture - so you can see how the ears go from slightly below the nose, to the upper lid of the eyes in this reference, and the like.Your use of colour is really good - the only thing I would perhaps suggest is using less 'blacks' in the shading - use a more saturated colour, and have it more graduated as the shadows aren't that stark.Hope this was of help