Wicca is paganism, and is contrary to Christianity in virtually every respect. It is spiritually dangerous and should not be encouraged.
- If you should marry, do you want to raise your children as such?
I would flee from it and have a serious heart to heart talk with your beloved, perhaps even meeting with a priest together.
There is too much to include as far as doctrinal issues here but I would suggest finding a good book in a Christian bookstore that explains the ins and outs thoroughly. In short, Jesus is the only Savior and she needs Him, not the sky, earth, wind and fire. (He made those things by the way.)