I'm new, but I thought I better mention... possible trigger alert?
I hear you and I totally relate to your girlfriend. I go through something very similar with my husband all the time. I want to try and help you if I can. But I'll just say up front... when you're calm and away from your girlfriend, think about how much you're willing to take to try to help this person you love. Then think about how much you SHOULD take and think about the difference between the two. No one here can judge that for you. As a sufferer, I would want my partner to stick it out with me. But, of course you shouldn't let yourself be abused either!!! If it's a toxic relationship, then maybe you should get out. I can't say. But like they say on airplanes... put on YOUR oxygen mask first and then help others next to you. You gotta be able to take care of yourself first. You gotta take responsibility for diving into your girlfriend's problems (if that's what you decide to do) and just acknowledge that's it gonna be bad and do your best to love and help your girlfriend, OR just admit that it's too much to take and get out. Like people have said here, there's lots of advice on this website about getting out of abusive relationships, and I'm sure they're more eloquent and I'll leave it to them to give you more of that important advice. Take their advice very seriously.
I lived in an abusive household as a child. It was really bad. No one ever helped me. I finally got out when I was 20 years old and I spent years just trying to be normal, I focused all my energy on being a really good person and working hard. I was very successful... I had lots of friends, great jobs, lots of respect, I got married, I had kids. But then a number of new life stresses came along... I got married, I had kids (LOL ;D), grandparents died, we moved, new jobs, big promotions, a very sick child... just life, but like a hammer on me, one thing after another. And then it was one thing too many, one set of especially stressful circumstances and I cracked. I was exhausted all the time. I would freak out and start yelling and screaming about the stupidest, everyday things. I was completely inconsolable, there was nothing that would make me feel better. I would get freaked out by the simplest things... my husband would walk into a room and I would scream and start crying. Let me state right here, my husband's practically a saint, he's a good man and not abusive to me in anyway. But, you see, having any dark-haired man standing over me is a trigger. Sometimes just eye contact is a trigger for me! (I could explain that... but it's awful, just trust me, it's a trigger.) And when I get triggered one time too many, I just snap. I scream and yell and cry. Sometimes, when it's my husband that triggers me, I yell about how he didn't do this or that or he's never nice to me, or he doesn't understand, or he's never there for me, or he's stupid or mean or whatever. Sometimes I go ballistic and yell about how he didn't run the errand he said he was going to run. It's awful and stupid of me and I feel terrible and I apologize all the time afterwards. Then sometimes I just can't apologize anymore because I never wanted to say those things or do those things in the first place.
Over time, I've come to think of it like this... it's like there's this poison (all the pain of past traumas) inside of me and I have to get it out. And just like real poison, my body's reaction is to vomit the poison out. But this is a brain thing... so the "vomit" is all words, words that represent fear and anger and sadness and helplessness. So... maybe she's yelling at you about how you do this or didn't do that or whatever... but, if it's like me, then maybe she's just so filled with pain and fear that she's up to her neck in it and some of it just has to get out however it can. And maybe she hasn't really come to "know" her trauma and she's just "reacting" to it. Like, sometimes I can tell when I'm about to lose it, and if I get triggered just one more time, it's all going to come rushing out... but I can think to myself... my husband is a tall, dark haired man, but he's a good man, he's not the person who hurt me as a child, I'm safe, I'm in a good, safe, clean house, the doors are locked, I'm okay, this isn't like my childhood home, I'm okay. I can do that because I "know" my trauma. I recognize what sets me off. I've accepted that I can't just try to "get over it," that I'm messed up and I have to adapt to that reality. But maybe your girlfriend doesn't even have that. Maybe the poison just has to get out, and maybe you can just sit there with her and hold her hair, y'know? It's terrible for you, I know (and I'm not trying to downplay that AT ALL), but since she's suffering from PTSD, it's terrible for her, too.
Maybe your girlfriend just wants to put the past behind her, but then it all comes out anyways, uncontrollably. I went through years like that, where I figured I had suffered enough. I would be good and work hard and do the right things, and the past would be the past and I wouldn't even have to acknowledge it to myself or anyone else. Only, it doesn't work like that. Our brains don't work that way. They latch onto past dangers, and keep putting them on the top of the priority list to be checked for again and again and again everyday. And it's exhausting. It's exhausting to go through my brain's checklist again and again... is there a dark-haired man, dirty house, no food, no way out, loud noises, people upset, people staring into my eyes without blinking, doors unlocked. And each of those things on the checklist brings up a memory of my childhood. And before I can do anything each day, before I can tackle my own to do list... make the bed, breakfast, grocery shopping, watch a movie, I have to tackle my brain's safety checklist over and over and over. And deal with bad memories that pop up or use my energy to build a wall and push those memories away. And sometimes I crack and everything my brain is reminding me to worry about completely floods over me and I'm gone. Things are out of my control, and I've got to get the pain out, get something out, get anything out, or I'll drown in it all. So I yell at my husband about how terrible he is that he didn't wash the dishes or that he doesn't understand or sometimes how much I hate him. Because that's something that I can get out. Something that represents the fear and anger that I'm really feeling.
Over time, my husband and I have both come to recognize that there are times when I'm just vomiting out the poison, when I'm lost in the flood of pain. And he sticks with me. I don't know why. Actually, I don't think he should. I apologize a lot and try to do better. I tell him that I didn't mean those things. I know saying bad things to him hurts him a lot... but it's all outside of my control at times. I can make a thousand resolutions to do but, but when the flood hits... it's too late... I can't control it and I can't calmly say, "Okay, honey, I'm about to vomit up 20 years of pain, but it's not you, it's me. I can't talk about being beaten as a child, so I'm going to tell you I hate you because you didn't do the dishes. So just ignore me and hold my hand and stay with me if you can, because it's bad for me right now, but it would be worse if I'm all alone with no one to help me." But I can't say that... I just lose it.
And yes, there's this whole list of things to make it better... therapy will help, and meditation, and journaling and yoga and mindful thinking and exercise and more therapy and medication, etc. But none of those, or even all of those, are a panacea. They're not a cure all. Going through trauma is bad and it's going to stick with you for life. Maybe you'll get used to it and learn ways to deal with it and that's the best you can hope for. I'm still struggling. I try to use all the tools and I'm still struggling and sometimes the flood hits despite everything I try to do and I'm drowning in it all. But it's better not to be alone.
