Composition: get rid of or don't include the tree, in this case it adds nothing to the image - she has nice hair, so turning her a little more front ways would help fill out the crop shape and size that you chose.
Exposure: underexposed although, in a shot like this depending on your processing abilities, the background would be ok at the present exposure
In other words, had you exposed a little brighter, you could have brough down the background so she would stand out.
I noticed the underexposure as well...for composition...I would have positioned her face a little to the left more and gave a little more tree to the frame and less background leaves...just my two dollars...spend it how you wish
edit: just noticed someone mentioned too much tree...ha! well...differences are like opinions...they both lack the ability to produce viable offspring