Exposure, composition etc....look pretty good. I don't think you need quite so much space (background) behind her (on the right side) but it doesn't kill the shot.
However, her expression does sort of kill the shot. It's like she's saying 'why the heck are you pointing that camera at me?".
It's not necessary to have a smile in every shot for it to be good...but I don't think her expression here works.
Now, take into account that I don't know her. Maybe she always looks like that...or maybe she's usually sulking and this is close to a smile for her...I don't know. That's part of the challenge when shooting someone you know so well...it may mean something to you but it may not come across to others. That's perfectly OK if the shot will end up in a family photo album or on your/her facebook account. But when looking for outside feedback...it probably won't have the same impact on other people...whereas, if the expression had been 'better', I'd think that more people would be likely to like it.
But as it is, I think you did a pretty good job on the exposure. It's strongly back/top lit but you have great exposure on her face and even though parts of the hair are blown out, there is still plenty of hair that isn't.