The Terrorist

There is a terrorist in my house. Waging war on the peace and tranquility that I crave. I don't deal with terrorists. I will not bargain for the things that are taken hostage. Yet, every time I encounter the terrorist I'm left frustrated and defeated.
You might think that I'm speaking of the toddler in my midst. He can wage quite a war when he wants to. But his grabs for power don't faze me that much. I've dealt with his likes before and I can deal with him now.
It's Princess. The ultra-demanding, fit-throwing, doors-slamming, foot-stomping outright negative 5-year-old (really 16) girl. One minute she'll be her happy, pleasant self, the one we used to see all the time. The next she's demanding to have a pair of outlandish boots, or candy with dinner, or to stay home by herself. Not asking. Demanding, with a little stomp of the foot and a nasty pout on her lip. I was not allowed to talk to my mother that way. And I don't allow it either. But whereas I would get a spank if it continued, she loses a priveldge, which immediately refocuses the fit and now wailing about getting the priveldge back. It's an ugly and vicious cycle. One that happens at least 5 times a day. In the past few weeks I've taken to clasping and hand over my eyes and groaning when it starts. I've used a tone of voice in public that I NEVER thought would come out of me. And really, sometimes, it just seems like it will never stop.
Today I bought her a pair of Sunday shoes and a new headband while she was at school. Things I presented to her, which she received gratefully. Not 1 hour later she is waging an all-out fit about the aforementioned boots in the middle of a store (I was looking for a Christmas outfit for the boys). Incredulous, I had her give back the headband. Which turned the fit in that direction. Hello? Am I missing something here? I don't consider my kids spoiled, but maybe she is. Her favorite phrase right now is, "You always say no!"
The best thing about her behaviors, is that I'm enjoying her sweet moments a lot more than I did in the past. I know that when she hits her teenage years we're going to have to batten down the hatches. I remember Mr. M going through a similar but not so volitle stage around this time. We rode it out and now he's back to the 90/10 good/bad balance ... one I can live with happily. I just wonder if we'll all survive this one.
Are your girls the same? Or does mine have a vicious mood disorder (I've seriously considered that)??