Hmmm. Do you see how much drama you have been through in the short amount of time that you have known this girl? If she does not get help, which isn't likely seeing as how she does NOT want help, you are in for a lifetime of dealing with this crap! Do you really want to go through a lifetime of the game playing, the mind manipulation, etc? I think its a bunch of hogwash to give someone a million and one allowances for their so-called disorder. You are bending over backwards, excusing every little thing that she has done to you by blaming her PTSD. What are you going to do if you wake up ten years from now and realize she's just a conniving, manipulative b!tch, and it isn't her PTSD? (Which it may very well not be, as she has no diagnosis!)
Yes, I am a sufferer. However, I believe in personal responsibility and don't blame my behavior on my PTSD. I *know* that my disorder affects my behavior, however I have the power to choose to not treat those around me like crap, telling them I don't care about them, then I do, then I don't, blah blah blah. THAT is manipulation, pure and simple, and NO, being manipulative is NOT a PTSD trait.
You want to "fix" this girl in a way you could never "fix" your mother. I've run into this more times than I can count, as "fixing" people seems to be a predominantly male trait. Please separate yourself from this girl for good, and get into counseling of your own in order to move past the things in your own past.