How do you handle a mother who has never gotten over her resentment and hits below the belt in every fight?

I consider myself a very good girl. My mother got pregnant with me at 16, married my douche bag father (who is not in the picture) at 17, had my brother at 19 and was divorced with two small kids at 21. Despite the odds, I think I've been a pretty good daughter. I've never gotten into trouble (not even detention), I graduated as Valedictorian from my high school, and I am a completely dependent Nursing student in one of TN's most competitive nursing schools with a 3.51 GPA. My problem is this: my mother constantly picks fights with me. She calls me determined to argue with me and when I try to avoid confrontation, she twists everything I say into something new to be mad about. Then, her oh so famous line is to tell me I don't have a mother and to never call her again or have anything to do with her. Now, keep in mind that this is over STUPID stuff. For example, she called me about a month ago to complain to me about my stepdad. All she kept saying was how she's so unhappy in her marriage and how she's tired of being talked to like dirt (pretty ironic, huh?). Anyway, I am a firm believer that you should stick it out in a marriage and make it work unless there's infidelity or abuse (that is not the case here). So, I tried to calm her down and get her to see that what she was mad about was not a big enough deal to divorce over. That's where she turned on me, and suddenly I don't love her and I've always preferred my stepdad to her and it's BS because she's my mother, and he's not really anything to me. Psycho...I know. And here's where the real problem comes in. My mother LOVES to grab at the most sensitive, touchy subject possible and jab at it. In this particular instance, she hung up the phone on me right after threatening to kill herself. She knows that this was a blow below the belt because, for one, suicide is serious and it's not something that you should use to threaten people when you're mad. Number two, my best friend committed suicide only 1 year ago and she knows how hard that was for me. So, she only brought it up because of that. I stupidly forgave her because some part of me is hanging onto the romantic notion of wanting to be best friends with my mom (and when she's not being crazy, I'd say she probably is my best friend...it's like she has MPD). So, yesterday, she called me to talk about my little brother's football game. He did not get to play very much and she was extremely furious about that. So, she starts going on and on with excuses and conspiracy theories about why he doesn't get to play. When I try to calm her down by saying he's only in 7th grade (most of the 7th graders don't get to play), she says ';Well ****** gets to play an awful lot, and I can't help but think it's because ***** is a teacher at that school. The boy in question here is my boyfriend's 7th grade cousin and the teacher in question is my boyfriend's mother. When I defended the boy by saying I didn't think that was the reason he gets to play, my mom went off the handle. She starts screaming about how I would, of course, prefer my boyfriends family and how I sold my little brother out and then continued to just make stuff up that I had never said (my mom does this---she convinces herself of a lie and then I truly think she believes it)...when I get mad and say she's being ridiculous she just keeps on and one about how i don't love my family and then she crossed the line. I've been dating my boyfriend for 5 years and I really want to get married. Only problem is, he's not ready. This is really hard for me, and I deal with it, but it's a very touchy subject that we've been dating for 5 years and he still hasn't proposed. So, my mother starts screaming about how I can just stay away from her and the rest of my family and says ';Well i sure hope ***** does marry you....after all you're already shacking up with him and f***king him whenever you want. Too bad he doesn't want to marry you.'; To this, I finally lost my temper and said ';Wow. You're just a b*tch, that's what you are.'; (I firmly stand by that) So, now she is having my phone turned off and coming to where I work while i'm at work to take my car and leave me stranded (I learned this all from my stepdad) with no way to get home or to work the next day. And the worst part of the whole thing is she is running to my baby brother and telling him lies about how I don't love him and I love my boyfriends family more and causing tension for him on the football team and at school. I just don't know what to do. At this point, I really don't care if I ';lose my mother'; because I don't feel like I had much of one to begin with, but I am very upset over the thought that she's going to stop me from seeing my stepdad and baby brother. Plus, I'm stressed about paying bills with no way to get to work....any suggestions for dealing with satan's leading lady?How do you handle a mother who has never gotten over her resentment and hits below the belt in every fight?
I think your mom is jealous about how your life turned out.She wishes she couldve gone to college,and wishes she was as determined as you are at that age.Look at your moms life 2 horrible marriages,being a teenage mom,having to work hard for little to nothing.And look at your life,valedictorian of your high school,honors program in college,totally independent.She envies shes never done what you have done.So its apparent that your mom is totally jealous of what you have accomplished.She probably takes jabs at you to boost her confidence and make her feel better about her life.It'll be okay and put some distance between the two of you,maybe it will make her realize that its your life and not up to her what you do.Good Luck!How do you handle a mother who has never gotten over her resentment and hits below the belt in every fight?
Yes, stop talking to her altogether.
Maybe you haven't gotten to the mental health portion of your nursing program. It sounds like your mom has a personality disorder or a mental illness. Google them and see what you think. Maybe you can convince her to go to a psychiatrist for evaluation and treatment. Good luck.