I need advice., Is she really worth the drama? Options

[SAMANTHAfamous]

Well to start, I had this best friend. Well, at least I thought she was. But I'm not going to mention her name though. Anyways, we met last year and I sorta didn't like her at first, because many people told me that she was mean and a bitch. I didn't jump to conclusions, only because i've never met her. So after constantly talking and socializing. She admitted that I was her best friend. At first, I was just like "Ok, that's cool." But then I started to feel like she was mine too. After awhile, I got to know her more, but started to dread her too. She was threatening and confusing to me. Because she would be calm and nice to me. But sometimes out of nowhere she would pick a fight with me. We would argue frequently, and I felt bad because I thought everything was always my fault. I would always be the one to apologize, even when it wasn't my fault. I guess back then I would be too nice. But now i'm starting to speak out and tell people what I truly think. Well, my boyfriend is 'cousins' with her so she speaks. And I think our arguements affect him because he doesn't want us to fight. But I honestly think it shouldn't matter anymore. I'm tired of her putting me through a bunch a crap. Me and her just got into another predicament. I asked her a simple question and she turned on me and started to bitch and complain to me. Saying "I changed" and that "Everytime she tries to talk to me like old times, I'd rather talk about my boyfriend instead." Wtf? I don't talk about him all that much to her because I know it pisses her off. But she whines way too damn much and I don't want to deal with this anymore. A part of me still wants to be her friend but another part of me just says "f**k her." I don't know what else to do. I've tried with her. It's so foreseeable of what she does now. Even my dad told me that she was a bad influence on me. I honestly don't know what else to do. Am I really being the good person in trying to forgive and forget? Or am I bad person because I supposably start most of the fights with her?