Katelynn is 12 and I swear I'm going through that right now too. I just want to SHAKE her!
She makes me want to rip my hair out. Let's ship them off until their 14th birthday! You up for it?

Ahhhh! It's good to know that improvement is only TWO YEARS away. But, at least it's not permanent.
We try to focus on positive disciplining in our house. It's helped. I've tried to be more flexible where I can and when she shows more responsibility. But, it's hard when they constantly are defying you and disrespecting you. I KNOW what you're having to endure!
Stick with your guns, that way she knows you mean business and can't walk all over you.
Oh, and with Katelynn, it seems everything has to revolve around her, be about her, or focus on her, or everything is horrible and terrible. Do you have the same problem? Example: She invited 3 of HER friends to Zachery's bday party this past weekend. I could've KILLED her. What part of it's ZACHERY's Bday party is confusing???? Seriously!? She's going through a MAJOR selfish phase right now. Are you dealing with that too????