BR, I was responding to Lemon Curd, who indicates that his situation is like yours, but who does not have a thread of his own.
Like you, I've read a lot of threads here. Although my betrayal was long ago, I've carried pain and insecurity from it and reading here has helped me.
Like you, I've been dumbfounded at times by the decision of some BH's to soldier on, pushing that rock up that hill, trying to force R with a recalcitrant WW despite giant levels of sexual humiliation by the acts of the WW, despite years of DARVO and TT and contempt. I agree that your thread contains none of that, which makes your thread somewhat of a koan. Some threads present Gordian knots of tangled wreckage, almost impossible to sort out. FOO issues. Substance abuse. There are threads where the couple were "first and onlies", and now, after infidelity, the WW has experienced the numinent thrill of NSA sex, where the BH has not. Stds. Pregnancies. Etc.
I'm also mindful that there is zero sexual humiliation in your case. I think you said you were a college varsity football player. I reckon you saw as much action as you wanted to see in those days, and your WW's extracurricular sex was pretty plain vanilla. There isn't a sense that she gave another man something you've wanted but never had the opportunity to taste.
Yours is like a carbon fiber hunting arrow of infidelity, light and clean and efficient and sleek, expertly shot directly into the bull's eye: what is the response to a spouse who clinically decides to cheat for no reason other than she wants to cheat? No baggage, no wreckage, just the core question: either you honor your marital vow of fidelity, or you don't. There's no going back. Once the promise is broken, it is broken. That will be true. Forever. And the promise breaker proves by her actions that she is the kind of person who will break a promise. Would you trust such a person a second time? Would you risk a future like Charlie Brown and Lucy with the football?
I don't pretend to have an answer. I try to put myself into the shoes of posters, to imagine what I would do, but of course that's impossible at some level because I'm not in your shoes, nor those of Lemon Curd. Further, we only know here what you post. We don't know the flesh-and-blood people involved and cannot read the unspoken nonverbal communication. For example, in your case, maybe it wasn't really just a clinical decision. Maybe she was having a mini mid-life crisis, that moment when a person looks in the mirror and sees a stranger in the wrinkled face looking back, maybe she was terrified of losing her youth and responding to something that made her feel young again. They say, "Inside every old person is a young person wondering what the heck happened." To me that would be easier to understand, and to feel safe from, because she could recognize that pattern in herself, understand how it led to her decisions, and break that chain of thought on a going-forward basis.
What I'm suggesting -- and I am truly not challenging you nor bickering, I'm actually trying to be helpful -- is that perhaps one step is to have her do some work to figure out what is wrong with her moral compass that would enable her to make this decision. It really is a binary issue. Either you choose to cheat, or you choose not to cheat. I've been married to my current wife many years. My work involves travel to trade shows and such, hotbeds of infidelity. I have a child who played teenage sports at a high level, involving many trips to distant places for 4-day weekends at college showcase events and such. Parents in those circles become clubby. They sit around the hotels at night drinking and flirting. Also hotbeds of infidelity. I've seen it happen again and again. I personally have had multiple opportunities. I always chose "no". Promise keeper.
It is possible via lifestyle changes to erect prophylactic barriers that prevent her from being in situations where she could be tempted to make this choice again. However, as I and other posters have pointed out, a lot of married people find ourselves in circumstances where extracurricular sex is easily available and highly attractive yet we choose not to engage, because we promised our spouse, in our wedding vows, that we would not. Promise keepers versus promise breakers.
In my effort to imagine myself in your place, I'd rather be a husband who believes he can trust his wife, no matter how much temptation is around her, as opposed to a husband who has to remind her that there are boundaries to what she can do because some activities are likely to get her in the presence of toxic people, drinking, partying, hotels, and offers of sex. I'd rather not live with gnawing doubt every time she is on the road without me. To return to the alcoholic metaphor, I'd rather live with a spouse who is in active recovery, as opposed to a dry drunk.
[This message edited by Butforthegrace at 12:34 PM, September 27th (Friday)]