The proportions look fine to me, though I don't think there would be quite that much space between your nose and lips. It looks like it has a lot of potential. My advice as of current is to put it away (I'm assuming you're done with it right now) and go back to it later so that the image will be fresh to your eyes and you'll have an easier time finding any faults that don't appear to you now.
(And don't worry, I'm not being mean by any means so don't take what I say the wrong way. I'm an art student myself and critique's, depending on your instructor and classmates, can be quite brutal and hard to sit through. It does look pretty good from my standpoint, just keep it up and keep practicing.)
Practice does make perfect.It still looks really nice.
When did you draw it?
Your subject looks a wee bit sad. I know! Try drawing her in a picture with,,, umm,,, Dexter! Yeah, and see if that makes her happy!
The g Factor is to be God-smacked...