It feels like I should just be able to talk through the issues with her and weight the pros and cons and we should be able to work it out. She has sat and thought about this decision for a LONG time and has not come to this point lightly. That kills me that she has come to this conclusion in her mind.
It's frustrating that we sometimes have to lose a thing to realize what we had. When I walked away from my ex-wife, she begged and pleaded and promised anything. I'd been trying to fix us for 6 months with little help, and even a small step on her part would've kept me around. Once I walked away that was it. I decided I shouldn't have to threaten D to get my needs met in a relationship. As you say, once they walk away they are not in the same place as they were before they walked away, and her exit affair is now its own obstacle.