I'm EO, so here's the answer I'd give from that perspective.
Having a dream, or a thought about someone else like that is not sinful. It only becomes sinful when we give it purchase in our lives, by dwelling the thought or dream, thinking about it, obsessing over it. By dwelling on it, we give the enemy a foothold into our lives, and that we should avoid always. In another thread, someone, Milovany maybe, mentioned mentally handing over one's bad thoughts to Christ to hold, thus freeing us from worrying about them anymore. Don't be ashamed. Just reject the thoughts and go on. :grouphug: