Something else to consider. Her Bible says "There is nothing hidden that won't be revealed." If you marry and If by some miracle she is not disfellowshipped she might always wonder when she might be found out. Not a good start for a marriage.
To me, she must learn to accept that Jesus' sacrifice paid for her sins. She needs to be helped to reason that the sacrifice is enough to put her right with God. There is nothing she can add to it or works she can do to be "more" forgiven. No meetings she can attend or amount of hours she can preach to buy her salvation.
Mind you, I no longer believe in Christianity AT ALL but if a person does, either the ransom is enough or it isn't. Simple as that. How many churches did Jesus build?
She needs to leave JW's for you two to be happy. So my final question is: If she remains a fearful believer, how happy can she be if she becomes what the Bible calls "Unevenly Yolked"? How happy can you be if she is not happy?