Since you are so willing to open your life & marriage commitments and "rules" so openly and imply that if others do not follow the same rules their marriages would not last, I thought I'd respond with some thoughts of my own.
First of all, it sounds to me like your "friend" is simply a




. That's the only kind of woman
I know of that sets out to sleep with others peoples spouses. If you do not trust this woman, this "friend" around your husband how on earth can you sit here and call her your friend?
I'd be a bit more concerned about letting her interact with my children.
If a husband can't keep his penis in his pants because a beautiful woman comes on to him he is a pretty sh!tty husband. If a woman has to control who is "allowed" or "dis-allowed" in her husbands life as her means to keep him from cheating on you, your marriage is in BIG trouble... and I mean HUGE.
What about trust and respect and commitment and love? If a marriage has those things (as well as sex, obviously) a man will not look outside of his relationship to have those parts of himself filled. Men who cheat are not always just after sex...
many just want someone to talk to, to share ideas with, to be with a person who makes them feel as if they matter. They want to be held and they want to hold. They are looking for what they
once had with their wife.
This does not mean that I believe for
one second that their aren't men (and women alike) looking for pure recreational sex for sex sake. I realize some just succumb to the biological predisposition to mate. I realize that some men (and women alike) are simply scum and will cheat until the day they die but those people, IMO come with other disfunctions that are easy to spot. Those types of men have patterns and a smart, intuitive woman can pick up on them easily.
No way should a woman have to spend her life "watching" her husband and her "friends", invading her husbands privacy and having hers invaded as well. A couple of he rules you and your husband live by seem to me rules made by people who have once cheated and are determined to not let it happen again. They seem possessive, over the top, controlling and plain ol' unhealthy... kind of like the "rules" we often see in domestic violence cases. If you cannot trust that your husband can have lunch in public with a female co-worker without that somehow leading to an affair, I strongly suggest therapy. If you do not trust your friends around your husband when you are not there perhaps it's time to look into the "why" of that?
I really hope you don't take this post as me dissing you because I'm not. I feel sad for you and I want to hug you. You shared with us to the extent of
telling others that their own spouses would cheat if they didn't do things your way. Perhaps your way is the faulty, unhealthy one?