Normal for her age.
To keep my sanity, (2.5 year old girl, very determined and stubborn by birth/nature) I shifted how I perceive my role in her life. Instead of punishments for being bad and incentives for being good, we've shifted to trying to work together. Live consensually. We talk about the behavior and what should have been the correct course of action. We've become her guides rather than authoritarian parents.
Instead of punishing her for hitting our cat, we talk about how we feel when we've been hit. And I ask if she thinks the cat would LIKE to be hit. Then we have her go pet the kitty nicely. This usually works for her because she's starting to make those connections that she has an effect on her world.
Alfie Kohn wrote a great piece about classroom management that I more often than not have been applying to home life:
http://www.alfiekohn.org/teaching/ditpnts.htm
We're trying to model behavior we want to see in her. And when she's old enough, she'll participate in how she thinks we should discipline her for doing thinks she KNOWS are contrary to how we want to live.
Now, there are some instances when she's just being a pill and doesn't want to listen. And 98% of the time I can pinpoint it to being tired or hungry. She then either rests or eats and life continues on as normal. (Which means there's something for her to eat in the car when I pick her up from daycare.)
Also, if I'm stressed, she acts out. And if your daughter has food sensitivities/allergies, including artificial coloring, THOSE can make her act out or trigger it.