She says she knows 'why' but all she comes back with are circumstances such as feeling lack of attention etc.
In my opinion, it is imperative that she keeps digging, for the exact reasons that you just stated. You have to know what's broken before you can fix it. In the same way that a surgeon needs to know what part of you needs surgery before he starts cutting into organs willy-nilly. Yes, the process can be very hard and very scary, and it is safe to say that sometimes the person doing the digging needs external help going through the process, because when part of the problem is that you lack the very same healthy coping skills that you desire, those same broken skills can continue to poison everything. In other words, a person with bad eyesight would have a very hard time making themselves a pair of glasses. Once they have the right lens to see things through however, everything becomes much clearer.
If you don't get why you did something, you are likely to do it again
Exactly. And let's face it, this is not really a "don't do this exact thing" kind of problem. It's not like quitting smoking. The affair was the symptom, not the problem. The problem is that a WS lacks the ability to deal with certain stresses in a healthy way. Whereas you said, "I had all those feelings too and I had the opportunity. I didn't.", that is because you have some things your wife lacks. You have the ability to deal with being uncomfortable, or sad, or in pain, or unhappy, and still not be taken down completely by those feelings. Instead, you can see these things as a moment in time, a challenge to be overcome, or simply something that must be endured and doesn't need to be given any more thought than necessary. In other words, when something like D-day happens, it still hurts like hell, but deep down, you know you'll survive this, and you'll be okay, and you are worth so much more. A WS on the other hand, would self-implode, see this as never-ending suffering and can't even imagine enduring this pain for 2 seconds let alone surviving and thriving despite it. The WS sinks into hopelessness and despair whereas a healthy person processes the pain and grows from it.
Anyway, yes, if the premise of her affair leads back to the fact that she can't cope with disappointment and pain, then unless she learns to do so, she'll just fall back onto the same old, broken coping skills again. Even if she doesn't cheat again, it still means she will likely just find some other unhealthy way of avoiding the pain and conflict. It's not about not cheating again, although that's certainly part of the plan. It is about removing the problem that caused the affair to happen, so that it never happens again.
She has been in IC for months and as far as she says has got nothing from it.
If it is still an option, I would suggest she keep trying new IC's. It takes a while to find an IC who you "gel" with, and many of them look for an "easy answer" or a "one solution fits all" kind of approach. Some make things worse. One of my first IC's told me, several months after D-day, that my wife should be "over it by now" and was just being a drama-queen (not her exact words). Several of our MC's seemed to just want to talk about me, and never even addressed ISSF's needs and feelings, as if she didn't exist or matter. (Not a great way to feel after your spouse treated you the same way). If her IC did nothing for her then get a new IC. Or take matters into her own hands. The "Why" article I wrote is a good example of something she can do on her own. Even if she's not an SA, she might want to try an SAA group, as a lot of them have similar backgrounds and FOO issues.
I kind of feel like some people create a false persona of themselves and after a good few years it becomes so ingrained, they can't even see who they were.
I think we all do this. My wife and I talk about what "normal" is all the time. I grew up being afraid, lonely and in emotional/physical pain all the time. To you, that probably sounds like a horror show. To me, it was childhood. It was my every day, and even though it hurts and sucks and I hate it, it is still the devil I know best, so when things are horrible, it "feels right" to me.
I believe that very few people in life would describe themselves in a negative light. I think we all see ourselves as "good people" if perhaps a little flawed in areas. The bad things about ourselves, we tend to minimize or compartmentalize or simply deny. "Sure, I might have a little temper, but if people would stop pissing me off then it wouldn't be an issue". In other words, "I'm just fine, and it is your fault that I treated you badly. I don't need to feel badly about it because it is your fault that I acted badly".
I know that for me, this is a big part of my recovery. I still believe I'm a good person at my core. I do have a hard time reconciling some things that I've done or still do however. It's not so much that I don't recognize what I've done or why, it's that my core processing gets in my own way. I grew up as a victim, a real victim. Similar to a BS, I trigger, and when I trigger, I protect myself. Since my abuser was someone who abused me verbally, physically and emotionally, I see even the smallest amount of conflict as something that should be responded to by protecting myself. Which makes perfect sense of course, in that situation. But in a marriage, especially one where I've managed to come full circle and become the abuser instead of the victim, getting defensive and attacking my (perceived) attacker (who is now actually my wife and the real victim here) is the exact opposite of what I should be doing, or how I should be feeling. It just makes things worse for everyone involved. I think most WS's fall into this same pattern. Part of getting through this, as a WS, is to see the "real you" in the mirror, and that "real self" is often so hard to accept as ourselves that we deny it to the point of our own detriment.