I know what you are going through. I love my wife so much, and want to feel loved back by her, but I dont get it very often, mostly put downs, and push aways when I try to hug her.
My wife also had PTSD before I met her she has had it for six years now, but from what you have described of your girlfriend, she seems to suffer worse than my wife does. Is she going to treatment? Has she had treatment before? My wife told me that she was worse than she is now, and that she cried a lot, she takes her frustrations out on you because she probably feels safe with you, she knows that you love her. Maybe if you just try to stick it out a little longer she might get better. Hopefully one day they will find a cure. Executing child molesters and rapists would be a good place to start. Good luck to you both.