Big 3 year old = big headaches

Well, Jillian turned three on Tuesday. I was really hoping that some magical transformation would happen once she reached that milestone.... it didn't. I can't figure that girl out for anything. She is defiant, bossy, destructive, down right hateful at times, and the only child I know that will whine and (literally) scream about EVERYTHING from the time she wakes up to the time she is FINALLY in bed. I have tried just talking to her, time-outs, spankings, taking her favorite toy away for a set period of time.... nothing works!! I just thank God that Tyler never gives me any problems. If they were BOTH that way, I'd commit myself! At first I just told myself that she's acting this way because Joe is gone and it's turned her world upside down. But the simple fact is.... she is old enough to know better. If she had just turned 2, I would say that she doesn't know how to express herself. But she has been acting like this for (honestly) about 5 months now. So Joe being gone can't be the cause of all this. Granted it has gotten WORSE since he's been gone, but I'm not about to just let her get away with it. She needs to understand that her behavior is unacceptable and she will receive consequences for it. And it's not just me.... even the babysitter is about to pull her hair out! I just don't know what to do.