I think its a pretty good sketch except that the nose looks a bit crooked. It seems like the features don't line up correctly. The bridge of the nose stciks out too much and should be sloped in more, if that makes since. The expression looks a little odd too. She looks like she is gisgusted by something. Teeth are hard to draw, i usually just make sure the person I'm drawing has a closed mouth. If you fix that and then throw in more detail and shading, i think it would be a nice portrait!
"There is no such thing as bad art, just bad artists."