What can I do about my mom reading my Facebook messages?

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My mom made me give her my Facebook password and she said if I didn't she would disconnect the internet and delete my account. And now she has been reading through my messages (she told me she did) and sometimes I talk about uh, personal stuff with the guy I like and I don't want her reading them and she said if I delete my messages she's not going to be honest with me about anything anymore or tell me anything WHAT IS HER PROBLEM? I tell her most things in my life and she said she "wants to know what's going on in my life" even though I tell her most of it! I want my privacy sometimes, you know? She also sent a message from MY ACCOUNT to the guy I like that was really weird and made him get mad at me, and he didn't believe me when I said it was my mom. How can I fix this??????