OneStepOut, not sure if this can help, but I will relate my story. I was never a witness and for a while before and after I married my witness wife she was essentially one step out herself. I considered myself a spiritual but not really religious Christian and was quite happy with my faith and felt that she could find happiness in hers as well. I did not know better, I encouraged her to study and ask the elders all the questions she needed. I even studied with them and went to the meetings. She also went to church with me but always kept pointing out everything that was wrong with it, as an aside.
Obviously, if I had known then what I know now, I would've never encouraged all of that and I would've never went along with it. Instead, I would've kept her busy doing all the things she liked and not doing witnessy things. She loved throwing birthday parties, celebrating holidays, and all the other things the Watchtower forbids. She was unbaptized so she would've had no problems maintaining family contact. Now she is baptized and STUCK and I now have to deal with a wishy washy woman who is hot and cold when it comes to her following her religion and walk on eggshells around her family as I cannot let it out that she still celebrates the holidays and throws birthday parties.
My advise, take your stand. If you know the truth about the truth, inform your fiance.
BTW, I like your avatar. I use to like Sailor Moon back in the 1990s.