What does this nightmare mean?

Are you serious? Is there a deeper meaning? Of course there is! Don't believe anyone who tells you there isn't. It means that the two of you are on conflicting sides, in a very serious warfare (that between right and wrong, Heaven and Hell, God and the Devil...take your pick); Surrounded by demons, and seeing your fiancee demonically possessed, you still chose the side of wickedness, which was a bad choice to say the least. Anything that scares you in a dream, especially a DEMONICALLY-POSSESSED fiancee, is NOT of God and should NOT gain your allegiance, especially if you don't even trust it. You should beware that the meaning of that dream does not come true; realize that it was an attempt to get you to choose the side of wickedness, and if you do, especially if it's just for the sake of your boyfriend, then you're in serious trouble. It's no threat, trust me; it's a warning.