What do I do about my stepmom?

Respectfully tell her you have made up your mind and you will be living by yourself, wherever you choose. My Father is the same way about things. He just HAS to have his way. The only way i was allowed to move out was to calmly tell my Dad I was moving out and my mind was made up. He got pissed off at me but eventually calmed down. I'm so happy to be on my own and believe me, my happiness was worth the argument between me and my father.