Take the hits and keep moving forward.

[azguy]

I'm so sorry to hear this. I can't imagine the emotions that must be swirling in your head right now.

This will likely take awhile for you to decide how you feel about this. Can I suggest an approach?

Thank her for being honest with you. Tell her you are still dealing with your reaction to it and would like to take some amount of time to consider it carefully. Then just go off and really think about how you want to respond to this. Be as open and kind as you can muster (think of her as the mother of your kids, if kindness seem wrong), but also don't try to discuss it until you can get your head straight.

Take your time with this news. Vent here if you need to. Hang in there.