Hi JPBill,
When I first joined a narcissism forum related to an X narcissistic dating partner I was with for 5 years, I absolutely hated when people told me to run, and that there was no hope... I was also terribly devastated by reading those words on the screen...
More than anything, I didn't want that to be the answer, but it was the only answer I was getting, over & over, from so many different, un-connected people, having no conspiracy against me
I rejected it for a long time, but kept reading the narcissism board daily. The more I read, the more I
painfully became open to what they were saying about staying away from my then partner, might be true...
If your girlfriend is narcissistic, or someone with strong N traits, it is likely that for as long as you are with her, nothing will change. Your level of pain, your being barred from expressing yourself, the irrational behaviors, the unpredictability, the knife in the gut cruelness, will continue on endlessly...
By its actual psychiatric definition, narcissism is a very rigid disorder, meaning it is extremely enduring, and very, very difficult to change.
At one time, I never thought I'd be saying the same thing to someone, and I dislike saying it just as much as I did not like to hear it...

But I do agree with the consensus...
If you are not willing to have this in your life ongoing, with no real end it sight, it really might be best to slowly begin to consider moving on....
I am so sorry for people who meet up with narcissists... They create soooooo much pain in our lives....
But when we finally heal from it, I believe we end up with more inner wisdom, and strength...
BT