My wife and I share with our friends about once ever other month. - you don't-thet is awful to do, that is not what a good friend would do. I sure as hell wouldn't be your friend.
It has been working very well for us for the last 25+ years.
You can't get her to do this but you can ask nicely and explain why you want this. If she's not into this idea at all you just have to leave it at that. We can't have all our sexual fantasies...