Just relax! I'm assuming she knows your a virgin. She most likely isn't expecting much. At the same time I bet it's just as special for her as it is you. And she gets the benefit of opening your eyes to the world of sex and experiencing all of your firsts. Also, talk to her about it! I mean your getting married so I feel like you should be able to tell her your concerns. I'm sure she'll be very kind about it especially if you guys are living in a more religious lifestyle. Also, just remember if you end up finishing in like 2 seconds take care of her needs too. Don't just be like well I came so it's over. As long as she gets an o too you should be fine.