I'm not qualified to determine whether your girlfriend is/isn't an N. What I can determine from your post is that it sounds as if you're in a lot of emotional pain. Frankly, it smacks of co-dependency.
In learning about N, I am trying to keep the focus on me. At first when I discovered this phenomenon (my counselor mentioned it during therapy) I went through the checklist of behaviors and said to myself "yep, yep, yep -- that's him -- he has all the behaviors or symptoms of an N." I read with fascination and it helped. But the healing, I think, will come from keeping the focus on me and learning why or how I gave someone else my power; allowed them to emotionally control me; and ultimately hijacked my life. There's a lot there to look at and the only way I'll not repeat this scenario is to acquire some self-knowledge.
Have you read any of the literature or viewed any of the sites suggested on either of the boards? They're full of information and could help you see through your situation.
Best of luck.