Ya know - and I know you're sick of changing it LOL - something was looking off, and I couldn't put my finger on it... but I think I see it now. I think the area between her nostrils, where her nose connects to her face, is a little too defined. I think if there was more of a gradual slope from the tip of her nose down to her lip, it would make a significant difference.
Bear in mind, that is JUST by comparing the above pics. Could just be a lighting difference.