@sandra35,
I have a 9 year old and my husband and I were just talking about this last night.
It's a source of stress that we have to nag her, on both sides. (We don't like nagging, she doesn't like being nagged.)
We talked to her about freedom and responsibility -- that we're happy to give her more freedom (especially, not nag her) if she takes on more responsibility.
I think you can do some natural consequences stuff too, depending on the situation. For example, if she won't eat, don't force it and just make sure there are healthy options for her to eat when she does get hungry... because she will.
I was also just talking to a friend who has a daughter the same age about how this is a really boundary-pushing phase. We were talking about it in terms of ending playdates/ social get-togethers -- they push, and push, and push, in a way they didn't used to.
At any rate, what you describe seems like it could be quite normal developmentally. I want to be careful to say that doesn't mean that nothing else is going on. She may well be stressed, etc., and this could be a symptom of it. But all by itself, what you describe seems pretty normal for that age.
Meanwhile, try not to yell, definitely don't beat her, and try to be very clear about expectations and consequences. Yet another friend (really, it seems rampant at this age) realized she kept bailing out her daughter when she would forget her homework at home (the mom would run it to school for her). The mom told her daughter look, I'm done doing this, you have to remember or else face the consequences. Her daughter forgot, again, and the mom didn't do anything about it, and the daughter felt terrible about not having her homework that day, but has been better about it since.