First thing i noticed when i saw this drawing is really strong shadowing and contour lines - two elements that make Dakotas face look much older than in reality. There aren't such strong borders between light and dark areas in original photo. Example for this is a single wrinkle on the right sie of the nose that in photo is hardly visible while in Your drawing is one strong dark line that adds around ten years to her real age. In the picture shadowing is also quite strong, but there is gradient between light and dark areas. Shadowing in Your drawing in some areas looks more like stencil. But this is one mistake that i realized. Except that Your drawing is good - proportions of face, detail and shadowing of eyes (this is very important and You made a really good job there), detail of hair, and another very important thing - emotions visible on her face and eyes. Just add shadows a little bit softer and Your work will be really good!
It's a good portrait but I do agree with the critique made below. To be fair though, that photo also makes Dakota Fanning look older than she really is. To me she actually doesn't quite look like herself in that pic.
I think you may have put too many dark shadows around the clothes - in photo it is a light lace but here it looks like a denser fabric that has been ruched. I think the hair needs thinner lines instead of so many shadows.