Jerome,
You must be crazy for your girlfriend to be attempting to change her but if at all possible I'd forget the whole thing and move on.
I too am not a witness and never have been. When I met my girlfriend she didn't mention the witness stuff for a long time and actually had not been active for many years. Everything was perfect and we eventually ended up having a child. We had agreed before hand that the child would not be raised a witness. Well... she has changed her mind entirely and now my life is hell (figuratively).
My point is that even though many leave they still hold the beliefs to be true and in many if not most cases I figure it's impossible to shake them. I've had witnesses come to the door on Saturday (for the benefit of my gf), had them in to explain their views and even though I have shown weaknesses in the points they are making they eventually say something to the effect that my questioning (more like poking holes in their beliefs) has made them feel stronger in their conviction. They are devoid of reason when it comes to their beliefs. Black, white, truth, lie... To question their faith is to question God himself.
All religions offer their believers a hope for something existing when we die. The real truth is that no one will know for sure what happens when we die until we make the trip ourselves. For witnesses that hope is more tangible than any other religion I am familiar with... living forever in a paradise on earth... some people need to know that this is what is going to happen, my girlfriend does and nothing I or anyone else says or doese is going to change that. To take that belief away she would have to come to terms with the fact that she might never again see her family and friends that have already died. Why would she want to take away a warm, fuzzy feeling like that?
Sorry if I sound bitter but the simple fact is that I am! Trust me Jerome even if she leaves there is no garentee that she won't go back. What if you have kids? Would you want them raised as JWs? I have friends that are witnesses, they're great people and I enjoy their time but after researching a little bit I always wonder if they don't stay friendly with a worldly guy like me in the hopes that one day they will be able to start a bible study. You know this is always on their mind... they love penciling in all those study hours on their little witness calendars.
Cut your losses and leave now.
QO