Oh man....do I feel your pain!!! My husband has told me things that he's never told anyone....and to be honest, not even remembered until now. It's a very lonely feeling loving someone with PTSD or C-PTSD in our case. After one particularly "bad week", when he finally broke down and told me what had happened, my first though was "woah". This is way bigger than him, bigger than me, bigger than the both of us put together. I felt so out of my element, and didn't know what to do.
I ended up reassuring him that I loved him, and that I didn't know what was going to happen next, but I would be there with him. I also told him that for our relationship to survive, we needed outside help. At that point, and with his permission, I spoke to a psychological associate that I work with. He gave me a few pointers, and helped me put a label on it (C-PTSD) and when I told my husband (and he was able to google it in his own time, in his own comfort level) it was like a whole new world. Not always good, but for sure new. His comment was how uncomfortable it was to see himself in print on the internet. His symptoms, feelings, experiences....textbook. I think that gave him a little comfort, to know that he wasn't alone, and that there was help out there for him. It has taken from January until now (on the heels of another meltdown) to agree to go to his family physician for a referral to a psychiatrist/psychologist.
In my experience, it's slow, and scary and it's baby steps. Maybe plant the seed and let it grow? Give her some information, tell her you think this may be why she is suffering (cause we both know that she is) and that you want to help her, help herself. Maybe if she gets used to the idea (in print) it will be easier to make that next step.