hi J., another J. here;
my 3 yo son is a lot like this and also has recently had some hostile behavior problems due to jealousy of our 16 month old, and also stress when we moved to a new apt.; but he has radically improved recently with the following changes by me and my husband.
number one, huge amounts of positive reinforcement. 3 yr olds are so bizarre, they talk a lot and seem sane and logical but they are far from it; they really are still babies who don't even know what's going on quite often. yet at other times they are so quick! they need a LOT of TLC and there's no harm in pouring it on. we give huge amounts of hugs, kisses, I Love Yous, You Are My Number One Boy, and constant concrete complimenting on even the smallest details, like, you are sitting so nicely in that chair! what a good job eating your cereal just like a big kid! you had a great bath tonight, good work, etc. His face glows when we do this and it helps him be nice.
number two, DON'T COERCE. my husband discovered that if he wanted my son to do something like get his pajamas on after bath, and my son would run away, it became a game we could not win, the more we insisted the more he ran away. so after one attempt now my husband will just turn his back on him casually, sit on the floor with my sons books and toys, and be kind of loose and open but not obvious. usually after 2 minutes of this my son will come right over, get involved, and transition right into pajamas.
another thing that works in the above scenario is role playing. after one attempt, i will say to my son, "Gee, I wonder if you'd like to pretend to be a big kid. Oh, big kid, would you like to show me how a big kid puts on pajamas?" and he will also come right over. these methods take all the heat off the kid and all the angst out of you.
also, don't invest what she says with power; she doesn't know what she means when she says she doesn't want to go to school, obviously she likes school. she knows that saying it DRIVES YOU CRAZY and gets her a LOT OF ATTENTION FROM< DADDY. that's why she's doing it. she will only stop if you ignore it.
i would reccommend looking up the "1-2-3 Magic" behavior program; it is a book which my husband and i got from a family therapist and we are putting it into practice now with wonderful results. it's all about your own sense of control and getting the child's respect through consistency and calm. you will love it. you do not need a therapist to use it, we just started with therapy for my son and this is where the therapist took us. it's really working and all you need is the book and the comitment.
good luck!
J.