I am having issues with a coworker, how should I handle this?

[Lynn]

This girl I work with has a major attitude problem and has a snappy tone anytime I talk to her...I have always been nice and polite to this person and have never talked bad behind her back or done anything for her to have a problem with me as far as I know. A couple other people at work have mentioned her having an attitude with them as well, including my boyfriend who works there too. Well, the shit hit the fan on Sunday when I confided in someone I thought was a friend about the situation with the girl always giving me an attitude. I specifically asked her not to say anything, and no more than 5 minutes later she is talking to the girl about what I said. Then, she posts all this negative shit about me and my boyfriend on facebook, calling me a bitch and a crazy ho and saying my boyfriend has his head shoved up his ass! Not to mention my boss who I was close with, is commenting on her post and basically siding with her. I am so pissed off and upset because I haven't done anything to this person, my boyfriend has never even talked to her aside from one time at work where she called him from returns bitching at him about being a door greeter and now I feel like people at work who I thought were friends (who I've worked with for years) are backstabbers and can't be trusted since they seem to be taking this bitches side. It takes alot for me to control my temper when someone has done me wrong and I feel like I am not going to be able to refrain from cussing this bitch out at work. I don't know what to do about the situation and I also don't know what her vendetta is against me and my boyfriend...