Is it my mother? Or is it me?

Hello there, let me give you some background info. I'll try my best not to bore you. I'm Jenny and I am fourteen years old. My mother and father divorced when I was very young, I was about three. Since then, my mother has remarried. I have an older brother and an older step-sister.
I believe my mother is bipolar. My family and I do everything we can to make her happy, even if it causes us stress or pain. But its for nothing, she'll find a problem in everything. My siblings and I are pretty intelligent for our generation. But I am going to a gifted highschool that is very selective and competitive. Since I've been there, I've been exposed to different culture and learned a lot about the world. This is not good, you see. My mother is a closed minded, conservative, bible thumping Christian and my artsy-ish interests do not please her. I am, thus, the target of her hatred and can do nothing about it.
I get to school at 7;30(right when they unlock the doors) and I stay till 5;30(when they close) just so I don't have to be at home. She thinks I've changed into a closed minded, ego-maniacal antichrist. I can't have a conversation with her without her telling me how much she despises me. Whats worse is that she's never, in my entire life, shown compassion. Even before I got into this school. But she's never actually hated me.
Apparently, listening to any music besides country, wearing clothes that aren't from aeropostale or abercrombie, not making straight A's, and questioning things before devoting your life to them label you as a failure. She hates me for not being her.
The worst part about this is she has mood swings. After she screams at me till i cry, she'll be laughing and smiling with the rest of my family. But these periods of happiness are fragile and shortlived. I calmly and respectively told her that I didn't want to go to church today, and she looked at me with pure disgust in her eyes. She said she couldn't believe how much of a failure I am. Took my phone(I wouldn't care too much if it didn't contain my iPod), took my posters, and makes me wear khaki pants and a white shirt to school every day.
I don't know what to do. Maybe I am what she says, maybe she's right. But I can't take this punishment anymore. Its been going on since I was little and the mental abuse is taking its toll. Please, help me. Or tell me how to change who I am so she will at least look at me again.