I was an active [although no longer committed JW] when I met my WORLDLY wife to be. I came under intesnse pressure that she should either became a JW or I should break off my engagement. I refused so we had a civil wedding [she's Catholic and I wasn't going to convert that way] and stopped going to any JW meeting etc [the big fade]. My Dad was reprimanded fro attending our wedding so that pretty much finsihed it for me. 18 years later my parents still don't really accept I'm nop longer one of them, and I have to regularly remind them to not preach to my wife, me, or our kids. However I don't want to be a witness so this works OK - their is tension at time though - no Nana and gradpa at birthdays, xmas etc.
If your girlfirend can accept there is a life beyound the JW's [and if she is at all open minded checking out some of the facts on JWfacts.com may assist make her mind up] then it may be worth keeping the relationship going.
However if she wants back in then you may be best to look elsewhere. They may demand she no longer associate with you to prove she has changed her eveil ways, and if you were to marry her 1st, and she went back it would be easier but you would always be the "opposed husband" - JW speak for a non JW husband. Also if and when you had kids there would be further tension and issues, do you want them brought up as JW's, she would have to raise them as JW's in spite of any wishes, you, the opposed husband may have. This could even be grounds for a separation if you insisted they were not to attend meeting, preach door to door etc.