Forget realism.
Play Street Fighter. Nothing they do is realistic. Everything is exaggerated. Realism does not make for interesting animations.
I like this, but I feel that you could work on the exaggeration a little more. It feels too hard as a whole, as if she was made of wood. Make her move a little more! You can't fight when you are so hard, realistic or not.
Good work. Although I don't quite understand the way her legs are moving. It doesn't seem like a realistic fighting stance. Her hips appear to not be moving at all, yet she's twisting her knees and feet, especially on the right leg. Try doing this yourself. It doesn't feel natural, and you don't often see fighters move like this.
I love Street Fighter. Though I don't remember seeing anyone move their legs like that.
http://us.bestgraph.com/gifs/s_fighter-1.html
http://www.fenrir.finalfantasyq.com/battleground/ssf/a.html
A fighting stance animation tends to focus more on the vertical bounce rather than the twisting motion, as far as I can tell. That's just my personal impression though, and I'm not a skilled animator. So by all means, compare this to the Street Fighter animations.