My fiancee is "physically attracted" to my best friend. Need advice.?

I introduced my fiancee to my best friend at a party about four and a half months ago. He has always been the ladies man. In high school, he must have slept with half the girls on campus. Knowing this, I was a little uncomfortable with introducing them. But I trusted her, and I knew she would never leave me hurt. Especially not for someone with quite as much...mileage. And he's been my best friend since the 6th grade. He's been a loyal friend. Later, as the weeks went by, I noticed that they were very.. chatty with each other. They were becoming pretty close friends. I was okay with it, because after all, he is my best friend. A couple weeks later, she has a dream about him. About them making out. This concerned me. But she reured me that it was completely subconscious, and she has no feelings for him at all. But then, about 4 weeks ago, he calls her drunk, and says "I think you're really attractive...blah blah blah." I don't know what else was said. Nor do I want to. Ever since then, she hasn't spoken to him, txted him, seen him...nothing. And things were all good. Then, 3 days ago, she had another dream. This time, it was about her leaving me, throwing our engagement ring at my feet, and running to my best friend. And last night she told me, that she has had ual interests in him. She says that she has imagined having with him. And that she has had these feelings for about 3 weeks. But, she also says that she loves me, and no other. That I am the only one she has eyes for. And she says she is truly sorry and is "trying to make these feelings go away"... but it is still there, in my head. I still can't help picturing the two of them together in my mind. I know she still wants him. And it's scaring me. I need somebody's help. Should I forbid her to be friends with him? Should I confront him about it?