So my wife and I have been together a total of 13 years married for 10 I know she loves me of that I don't have a question but a couple years ago we talked about it for a long time and decided that we were fine with an open relationship I (bisexual) had a casual fling with a guy who had been flirting and she had a male friend she decided to start sleeping with before long they were officially dating (keep in mind I'm supportive of it makes her happy) before too long into this arrangement my male friend has to move out of state and we break things off I'm now more comfortable with sleeping with women but she seems to get upset if I attempt to bring it up

Does anyone have advice for how to bring it up that would help her understand that it's JUST sex?