Welcome Batman89, you've been given plenty of good advice from folks that once walked in your shoes and know where you are. Seeing so many experiences of people that are further ahead in Life than you (due to age or experience) is fantastic for you. Reading all these comments is like having a time machine and traveling into the future, experiencing all the options. There are many possible outcomes of this, none of us knows the future, if you marry her - she could leave later on or stay and become even more fanatic - the spectrum will, maybe, be something in between.
No matter what, this will be linked with pain and heartache (losing the "Love of your Life" or losing yourself). You only have to chose one pain from the other. Only that one pain WILL fade (heart broken because of Love - I am 44 years old and know what I am saying, believe me) but the other pain (being in some group that doesn't share your thinking, losing your parents, not being yourself and the potential for even more fanatism on their part in the future) WILL follow you for years to come and have a bigger impact than you can imagine.
I had the very same conversation with my ex-wife. We where Bethelites for over 11 years and married for over 16 years. I talked to her and tried to convince her of the many lies (that she even knew where true, due to our time at Bethel) and yet it took a toll of 5 years of discussions and tears and a divorce. Me, not being able to see my little daughter.
As a friend: Don't do that to yourself! Please save yourself of even bigger pain. It's up to you and this will not be easy, but remember that you don't know half of the world. Have you traveled? Seen other countries, cultures? There are fantastic girls out there. I now have a GF that even didn't knew that Jehovahs Witnesses existed and she is wonderful, balanced and fun. My true soul mate. You haven't seen anything until you leave the cult and start an exciting, refreshing new Life. Give yourself (and her) that opportunity. If you leave her now, you still could have her later, but if you stay with her, you are shutting down the other opportunity.
Take a deep breath, plan the days and weeks ahead and do something you always wanted to do. Go out. Be social, ENJOY!