C, I think you're going to simply have to settle on an answer, even if it's one you make up, and then go forward, being open to her showing you something different if you need that option.
For example, what if I tell you that she did what she did for the sole purpose of getting another baby from you; that she was driven by desperation and didn't see any other way; that she said all those things as part of the "act", not realizing you would be so resistant; that she was even hoping that a miracle would happen and she would get pregnant the old-fashioned way; that her conscience kicked in or she exhausted her ability to fake it or she realized you weren't going to give in, whatever, she had enough; that she really is done but doesn't want to harbor anger towards you.
Does that "answer" give you the ability to move on?
No one here can explain it to you, and I doubt she can even do so herself. Mourn it and get back to living.
