I have been a non believer all my life and married a JW 22 years ago. She is still in the organization and I am very much against it. We have a happy family where both have had a say. She planted the religion, and I planted the desire for higher education in our children's mind. In retrospect, had I known this religion better 15 years ago, I would have never allowed the indoctrination.
These are different times. Information for you and your girlfriend is available everywhere. Use it. It will help make better decisions and plan your future better.
The main thing is that you research all you can about this religion and how it can affect your long term relationship with your girlfriend. If I can summarize it in few words, then: BE VERY CAUTIOUS