Letting my spouse have sex with another man

Hi, so this is my story need advice plz. I'm 35 years old & my wife is 30 we've been with each other for the past 15 years we have to bueatiful girls. So getting to the point I'm all she knows sexually she's never been with no one else except one time she gave one of my close friends a BJ in front of me she wanted to experiment something knew I was ok with that. Are sex life is amazing beyond amazing we have sex 4 to 6 time a week that's alot I think we are both nymphomaniacs lol!!! So the issue now is she is sexually attracted to an ex- coworker she's thrown me hints that she always fantasized about him, this guy is the missing link lol... No lie but for years I've always told her if you are sexually attracted to someone let me know and we can go from there instead of you cheating on me, I will respect you more if you let me know.so this guy is leaving in a week and a half out of state for good. So I ask her y him her response is he's the missing link and she knows he will be a good f*^€ so I can't argue that as funny as it may sound but she just wants to try something knew and this is her opportunity to not have ant strings attached or any sort in her mind she thinks that there might be a secret position or some kind of hocus pocus orgasm lol!! If you are wondering do I please her sexually I think I do I make sure she's satisfied before I even think about letting go. I'm very secure about are relationship jealous of course but not to the extreme. So I'm wondering if I don't let her have this opportunity she will end up doing behind my back eventually.. Comments advices plz thx for reading