Dinner with an Ex?

Say I went out of town with some buddies this weekend. I got back and saw my wife who mentioned to me, after the fact, that she had had dinner with a guy she had dated. What would you guys say? Now let's say that she wasn't my wife, but rather a girl I had been dating exclusively for only the past 4, 5 months. What does that change? See a year ago, I was engaged to another woman who cheated on me. I discovered, cancelled the wedding, eventually ended the relationship and then moved on. Eventually, I started dating my current girlfriend. But with that in the background, I felt this might be a good place to present the question. I don't want to project my xWF's betrayal onto this girl (or all women), but I feel like I need to confront this dinner in some way. I'm not worried that there was any actual betrayal here, but rather wondering how to introduce this girl to the way boundaries work in a maturing relationship. She's 10 years younger than I and probably believes that ex's can be 'just friends.' I sure-as-f*ck don't, not anymore. My xWF did something like this at one point as well, but we had been together for 3 years and were living together at that point. I, predictably, didn't make an issue of it. I'm looking to learn from my mistakes. The bigger question here is about making that transition from a marital relationship back to the dating world. Which standard apply and which don't yet apply? Thoughts?

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