It's a positive thing that your WW told you. A step in the right direction, albeit perhaps a baby step.
One-on-one lunch/coffee with co-workers is highly situational. In some workplaces it is common, especially where co-workers collaborate on projects, such as engineers.
However, in most office environments, this is not typical. People may do this in small groups, but not one-on-one. Based on what you describe, my gut tells me your WW's intentions were innocent; OM's were not. As another poster noted above, men will hover about like mosquitoes, sometimes for years, watching and waiting for their opportunity. She may have him firmly "friend-zoned" for now, and maybe forever, but he doesn't know that.
Thus it comes down to boundaries, as you note. A rule of thumb is that a person can't go wrong treating work colleagues on a "strictly business" level. However,there is a natural human tendency to want to be friendly with work colleagues, and I understand this. It makes the workday better in many cases if one is friendly with colleagues.
My wife works for a large company with a highly developed campus, including a food court and a coffee place, all inside the campus. There, coworkers often grab coffee together. It's different, I think, than leaving to workplace to go to, say, Starbucks. Still, male/female colleagues ought to be mindful of boundaries. I seem to recall you mentioning that things got personal and even slightly sexual between you and a female colleague at one point.
I get all of that, and I was able to temper my original reaction because of thoughts I had along the same lines - this is normal, no big deal, I wouldn't be upset Pre-A, she told me about it which is a big positive. What nags at me are two thinigs - 1, the minimization in describing him really bothers me, it implies she knows I would have been more upset if I knew what he looked like and so choose to hide that, and 2, the fact that she didn't just see him in the cafe and sit down with him (more understandable) but instead said yes to a walk from their office to the cafe, which is at least a quarter mile walk, outdoors and on what I would describe as a borderline romantic pathway (tree-lined, landscaped, like a college campus). Having now seen the path and distance, I am more disappointed that she ever said yes, although I'm sure to her having done the walk a thousand times it's a lot less "romantic" than it looks to me as an outside observer.
This latest experience is a double edged sword. She screwed up, no doubt. But she realized she did and disclosed it, which is good. We can potentially learn more from our errors than when all goes well and this will probably be the case for her with this situation. It sucks that the good part is overwhelmed for you by the bad yet that is how the vast majority of BS would feel. At least you weren't as angry as you would have been months ago... another good part.
I do have to push back on one aspect of this though. The idea that she was minimizing his attractiveness might be accurate but I can make an argument against it. If she was intentionally trying to minimize the fact she found him attractive, then why would she have offered to introduce you to him when you were on the campus?
It seems to me that she would not have pointed him out at all if that was the case. Instead, as you told it, she brought up the fact that here was this guy and asked if you wanted to meet him. I do think it is an interesting piece of data showing that she doesn't understand what might trigger you. But her entire offer to introduce you seems to fly in the face of the idea that she thinks he's really attractive and was trying to hide it from you. Does that make sense?
Of course we can also argue that even if she had no attraction to him, she subconciously sees him as attractive. Who knows. At least she realized it was wrong and stopped him the second time. It does sound like he might be intentionally stepping over the line with her.
If it helps, I will say that my wife isn't really the type to visually look at guys and find them attractive. We have discussed this a number of times. Attraction doesn't really work that way for her. She can objectively admit, yes, that guy is handsome but she mostly doesn't think or react that way. I am not sure if that helps or not vis a vis affairs. I think most affairs with women seem to sneak up on them. It isn't the visual attractiveness of the guy that does it. But putting myself into your situation with the perspective my wife has shared with me, I think I can believe your wife and the fact that she didn't immediately or consciously see him as attractive.
Did you discuss with her the fact that he could be seen as attractive by many women as being an extra trigger for you? Would that be helpful for your wife to understand?
I can imagine my wife reading your post and nodding her head vigorously in agreement, hah. I think she would agree very much with what you wrote, especially with how your wife perceives attractiveness. And I am not saying that I don't get it or that it's dishonest, but what I do believe is that anyone should be able to do what your wife can do: "She can objectively admit, yes, that guy is handsome." That's what I'm asking for, objective and honest descriptions. It matters to me whether or not the guy at work who is asking you out for coffee is objectively handsome or not.
She did tell me almost word for word what you said, which was that she offered to introduce us because she thought once I met him, I would see why she has no attraction to him. Apparently, she thinks he has an ugly face and a less-than-winning personality. I was too upset at the time to have any interest in meeting him, so who knows if there would have been truth to that. My internal dialogue was, "yeah, let me meet him now when I'm in this terrible mood, he'll think "your husband is an asshole AND unattractive to boot", then even worse than just hitting on you for fun, he'll feel justified in saving you from a life with me." Did I mention I know I have my own shit to work on?
We had MC today and my wife expressed how she feels like her simply being alive makes me feel threatened and that she has to "put herself in a box" in order to appease me. My response is that I don't feel threatened but I do worry, I worry about her getting hit on and pursued by men, and I would worry about that no matter who I was married to. The reason it goes from a worry to threatening is that I don't feel confident in her ability to shut it down. And when she says she has to "put herself in a box" and lose her own self-identity to make herself safe or what I need her to be, I think that is just catastrophic thinking and an unfair response to what I am asking.
Finally, after MC today, our MC said something which brought something to light for me which I hadn't really been able to name. He had emailed us and listed some areas he wants to focus on and one way "Concerns about immediate felt-sense of safety about the relationship (i.e. boundaries and autonomy) for both of you". A light bulb went off for me when I read this.
I think a lot of what bothers me about her behavior around the coffee thing is how much it reminds me of the situation where she cheated so many years ago. Instead of going out for coffee it was going out for drinks, but the gist was the same - she wanted autonomy to "do her own thing" and not feel kept in a box by me, and back then I gave it to her and trusted her, and she crossed boundaries and cheated. She also lied to me and minimized her relationship with her AP back then, and lied to me about the extent of what happened when I discovered some texts. My life has been radically negatively affected because of my wife's breaching of a boundary at work and deceiving me about it, and it triggers the hell out of me to think of giving away any more years of my life to a similar event. I recognize this is not apples to apples, but it brings up similar feelings for me. I don't think she realizes that.