Oh, god. I am so sorry to hear that, 62ford.
There are other TFP'ers who have gone through this, and who will be able to offer more helpful advice. I have not gone through it, so my questions are about what you both want right now: do you both want to try and repair this and continue the relationship? Marriage is not a thing to throw away lightly, though it seems she has already made that decision, but have you? Would you both be willing to see a counselor together, or do you truly feel there is nothing redeemable left in the relationship?
Did she seem remorseful, or was she just disappointed to be caught in the act? Why wasn't she communicating earlier about what she didn't feel she was getting from you? "Not wanting to hurt you" is not a good enough excuse, especially for confessing about cheating. At its core, that statement is pretty much self-centered... it means she didn't want to feel the burden of guilt on herself.
Uggh, shit I hate it when these things happen. I'm sorry, man.