My wife and I have been married 5 years, together for 8. We are very happy, do lots of things together etc. Although we haven't really been having sex for a while and I'm the one who always has to initiate.
About a year ago we made friends with a guy who we both really respect. He's a lot older than the two of us (over 20 years) and has helped us out for various things. The problem is whenever we go out (about once a week) and he's there my wife becomes extremely flirty with him - bedroom eyes, biting her lip, touching him. They banter a lot and he'll make semi inappropriate comments which she doesn't shut down. They text each other the day after saying "that was fun etc." and then he calls her to see if we (her and I) want to hang out again - but I suspect it's only to see my wife since he never tries to reach me personally. Last week I saw him parade her around to his friends that I didn't know, saying isn't she beautiful, look how gorgeous she is etc.
I told her after one particularly boozy night that I was uncomfortable with things and kind of lay all the blame on him. She defended him and said he's like that with everyone. I don't know how she can't see that it's inappropriate or why she won't try to stop it.