[[attach=183244]95585939.jpg[/attach]]
The biggest thing that pops out to me is a sense of tension that makes the smile feel less genuine. Specifically in the corners of the mouth, her lips look very thin and tight. Also, the creases that go from the top of the nostrils to the corner of the mouth need attention. Right now yours stop far to soon. Finally the sides of the nose often lift a bit and bottom teeth are often less apparent in a smile. Remember that it’s a lifting motion. To expose lower teeth requires a contrasting motion. Of the three, your middle is the most successful. Expressions are something that you need to go back to reference again and again. I’ve linked an image from Getty Images, but make sure to use many examples to give you a better feel for what you’re trying to do. Good luck, interesting character idea.