So let's see. Apparently there is sexual tension everywhere. I'll agree to that in part. Yes I feel physically attracted to some people but because I'm attracted to them and I'm engaged to someone else doens't mean that I want to go out and fuck them(because that's all it'd be) on the side. Now, I've been stupid in the past, but that has raised my resolve in being commited. I also do know that restraining someone from doing something is an ABSOLUTELY stupid thing to do because eventually there will be resentment. I don't care how you try to reason it, it will arise. I know if my fiancee said, "You can't go out with females to dinner or a movie." I'd be pissed, and I know if I pulled the same on her, she would also.
In previous relationships, my ex was hanging over all guys. I asked her to stop and if anything, she did it more.
I believe you go on a case-by-case basis. I would not have a problem if she went out with one of her close friends, but if it was some random guy, I'd be worried and I'd let her know but I wouldn't restrain her. I'd let her make up her own mind because that shows faith and trust in the other.