D.K.
Have you always given her boundaries? Making sure you are consistent and she has serious consequences, even if it means going to bed after dinner every night for a month it has to happen. Is she getting enough sleep? Is it something that just started? Could she have been abused somehow at school? Rule out everything that could set her off to this degree. Has she always been this way?
Being a stubborn and strong willed toddler is one thing but being so violent there are serious concerns needed to be raised. I would have her evaluated for learning disabilities as well. Some ADHD kids have these tendancies out of frustration they lash out. Not saying that is it, but sometimes other frustrations come into play with these type of behaviors.
If you are very consistent at home with clear rules, consequences for her bad behavior and zero tolerance for hurting another and she is still continuing I would talk to your Pediatrician about recommending a play therapist. It worked wonders for my daughter last summer when she had some anger issues due to my divorce and her dad moving out of state.
I have a difficult, sometimes overly emotional and sometimes smart mouthed 6 year old but with me learning patience, clear rules, consistent consequences it has gotten a TON better. My getting too out of control and losing my patience with her behavior made it worse. I became very concise, to the point and matter of fact about things. She has choices, if she chooses to act up, not listen and sass me then she will have consequences. No negotiations, not counting to three, no chances. It has worked so well in the past month I cannot even tell you it is like a new child.
Find out what she is angry about, then go from there. A behavior chart even to show her how she is effecting the family and see a visual of her behavior. For every infraction, even at school have a serious consequence. Something will matter enough to her to make her strive harder to do better.
For my daughter, early bedtime is a breeze to get things under control. She minds, listens and doesn't sass and life is calm, if she chooses to be unhappy and make everyone else in the house miserable with her fits and defiance, early bedtime! Three weeks ago she was in bed at 4pm, seriously!!! It was amazing how my sticking to my guns, even ignoring the fits and crying and being clear on my rules helped her realize she has control over what happens in her day.