Is it normal for my mom to be so involved in every aspect of my life?

[mangoooo]

I'm 15 years old and a sophomore in high school. My mom is OBSESSED with checking my phone and stalking my twitter, my friends' twitters, and all of my apps on my phone and my messages and pictures. I get grounded when I try to change my phone password and I'm on edge constantly, trying to keep her stable and keep myself from becoming hysterical. Every day she finds something new! Something mean someone tweeted about me, and she screams at me saying I'm an idiot for being friends with them last year. Some nights she sits on my phone for hours reading through every conversation (I didn't think it was an issue so I kept most of my messages from last year to the present,) and goes through all 1000 of my pictures and somehow finds a million things to go off on me about the next morning. I've been waking up to a furious mother, and I haven't said or done anything that isn't age appropriate. I don't go to parties, sneak out, or drink. I've never done anything terrible with a boy. And she doesn't believe me. I have straight a's and am a really good kid who has e erything under control. I understand that she "cares" but I'm honestly ready to do something drastic. I feel that I deserve my privacy and that my mother shouldn't spend her time obsessing over every little thing that I say and that people I know say. Please help me decide what to do, and understand why she does this to me.