You canwork on the white balance a bit in photoshop now that I have shown you the color balance, watch the apreture at which you are taking your photos, they are always softer wide open than stopped down a bit. Could have caused a bit of the loss of detail in this image. Good step in the right direction.
This is a nice portrait but she doesn't seem to be interacting with her environment. the punch on the bag clearly isn't a real punch and because she's looking away from the bag it just looks like a side note.
I'm also not fond of the shadow on the wall. Ideally I would like to have seen her interacting with the equipment more or even better a student and with more of the gym in the background.
The lighting is a bit off, or maybe it is the white balance. I would have liked to have seen more of her, maybe zoom out a little so that the heavy bag is more visible. The cropping makes her look rather short as well...4
this has a very snapshotish feel to it, as well I'm guessing you used the onboard flash which has created some harsh shadows. composition is slightly on the boring side as well with w kick boxer it might have been interesting to have a much more dramitc angle and pose for the photo.