I can relate. And while that doesn't help your situation directly, I think seeing the number of replies from people who let you know that we feel/felt the same way can make you feel not so alone.
You mention 'cheating'. Is that how you view it? You say you didn't mind her talking to him, but did you agree to her flying to see him. What was that discussion like? Was there any talk of what her expectations were for meeting him? Platonic? Hoping for more? Knowing there would be more?
Your talk of 'cheating' makes me guess that you thought she would not become intimate with him without checking with you first. How would she classify it?
In some ways, I like what redpepper said. I like how redpepper described the situation and what *should* be done. A LOT. (although personally, I wouldn't pay for his flight - if he wants to have a relationship with my wife, make some effort buddy)
**And it annoys me that the burden has to be put on the original mono primary partner.**
So she found someone else to love and take as a lover. Great. Wonderful. But hey, there's still this guy sitting at home that you've been married to for 10 years and have kids with that *wants* to be with just you. Wants to be with someone who *wants* to be with just him. Doesn't want to have to think about her wife being intimate with another man. It seems too easy to chalk certain unintentionally hurtful things up to NRE. It still hurts.
I think your screen name is appropriate.
I hope you find a path through this. There are plenty of success stories and I truly hope yours can become one.