I'm really angry..is it okay if my mom does this..?

My mom goes through everything, including but not limited to:reading my text messages, getting on my facebook and my myspace, reading all my personal messages on these sites, reading conversations between my FRIENDS on these sites and bugging me about them, trying to 'talk' to me about it, and going through my stuff. I'm afraid to keep a journal or a diary, because I'm afraid she'll read it too. Even if I get one with a lock, they are easily picked with a bobby pin. I believe she's read my past diaries I've kept. But now she's just being worse than ever. She found out something about me, that she'll never understand, but tried to act like she did. but I was really not in any mood to talk but she kept pressing it and pressing it and pressing it, even after i told her to forget about it. (She's been pestering me several times a day since that incident, no matter how much I tell her to let it go.) Then, over this same issue, we made a double-sided promise, which I intend to keep, but not two minutes after she made it, she went back on it. She broke it within 24 hours. I really trusted her, but now I can't even say that I love her. I'm really sad and beating myself up over this. Please help me!