Unfortunately, and to my huge disappointment, my wife seems inherently to be at risk for going wayward.
She may have already gone from EA to PA, especially likely if OM is a coworker.
The OM is indeed a coworker. They are in exactly the same line of professional work. She said a couple of months ago that she can "talk to him about anything and he really understands me". Implication: I am useless and insensitive. Sure I am not in the same line of work, but I am in another, equally interesting one. She doesn't seem to be really interested in what I do. I'd be delighted to take her on a lengthy tour of my world.
However, the way you describe your WW, it seems affairs are inevitable.
She might be inherently emotionally un-grounded, confusing attention/excitement for profundity and low-key, warm, sustained stability for dullness. I don't think I "entertained" her enough; but then again, she seems like she can only be entertained on her own terms. She's not "bossy" per se, but very particular about what she wants when she wants it (or doesn't want). She detests surprise parties for her, considering them to be an imposition. Nonetheless, she purports to crave spontaneity -- which I now think is a clever excuse to avoid being pinned down for social events she doesn't want to attend (usually mine). While I like to hang around the home as much as any happily married guy, I thought our social life was becoming a little narrowed/stymied by her.
I just yesterday recalled how she told me that a therapist she saw a few years ago (on a short series of consultations) said that she had a controlling personality and has a big fear of abandonment. There is something to this. Her father left her and two siblings when they were toddlers. Her mother (to mom's credit) stuck with it to provide well enough for the family on her own but kind of burned out in the process; once the kids were in college mom phased out herself to become a bit of a hippie loner. My wife rarely sees her parents or siblings, although one lives close by. I wonder how a non-family has affected her outlook.
She is very friendly and charming in small doses -- her colleagues and casual acquaintances just love her -- and I don't think this is fake at all. But she seems to have precious few real, solid friends outside of a narrow work circle with whom she interacts on a current basis. She also says very unkind things about such friends -- not even as a caring criticism -- often about their lack of ability or persistence or perspective.
Speaking of criticism, she is the original contradiction of "being able to dish it out but not take it". Even friendly suggestions are received like out-of-line comments. (I am not a back-seat driver at all, but occasionally do like to warn the driver if there is something coming that s/he might not see, like a pedestrian behind us in the parking lot of the mall. She told me not to comment on anything again with her driving, as she can see everything. Yes, she is an excellent and alert driver, but this attitude is uniquely over-confident and dangerous.) In many of our arguments, she refuses to try to see my perspective, because it's all cut-and-dried, and I am wrong, deluded, lazy, whatever.
Sometimes I detect a woman trying to be Superwoman, but who is overcompensating to the max at every turn: a hard-boiled exterior which might have a marshmallow trapped inside. But the confection isn't sweet and cute when you get up real close and take a bite -- it's sour and nasty.