This is actually a common thing that happens. In fact, it happened to me once. I was asleep and woke up having sex with my man unexpectedly. It freaked me out and I instantly was like "what the heck is going on??" I became defensive and kind of creeped out initially. But I soon calmed down and got over it. I have always been a sleep walker anyway. I talk in my sleep and things like that and never even know it most of the time. We can function on a subcontious level and never even know we are doing it. Especially when alcohol is involved. That makes it more likely to happen. Honestly, I think this is where some of the confusion comes in when a girl gets drunk at a party, the guy swears on his life that she wanted it, but the girl doesn't remember any of it. Sleep seems to have a similar effect on some people.

You should both do some research on this together and talk about the fact that things like that happen every day to people all over the world. It was just a misunderstanding of sorts and you didn't mean her any harm. I mean, if you had plans to get married, I don't think this should be such a big deal as long as it happened just the way you said. Keep doing all you can to reassure her you didn't mean any harm and how much you love her. I think talking about with a counselor could help. They could probably even explain to you how situations like that can happen.

Hope it all works out for you.