It looks way better after faust's point about the face shape. Did you say the girl was done without a reference?? Pretty good if that was from the head. Lets see how much more it could improve if I could find you a reference. Just looking at it, the first things which looks wrong is the nose and the forehead.
There are different types of noses, but there are no noses that curve up like a bowl at the bottom. You're missing the flaps of skin beside your nostrils. The deep shadow, you added, improved the depth, but the shadow you added wasn't correct. Now the nose looks like a narrow box on top of the face. Nose shadows are never straight. Because the nose is a gentle slant, shadows should be a slant too. The planes shouldn't be an abrupt change from dark to light on the nose.
Forehead, she has a massive one right now. See HEREwhere I put the red line, that's where the forehead should end and begin curving back/where hair starts. (please excuse bad photoshopping)
And for reference, not QUITE your head tilt exactly, but should be enough to see a reference for a real nose . click here
i'm out, sorry for taking so long to do a real critique. ;D been busy with school. I'm on holiday for a week starting today. so expect more from moi.