This isn't about fault for the affair or when it started. I wasn't even suggesting punitive measures. Maybe I gave a fair amount of my own bias in this, but my primary concern was what is best for you, not necessarily what impact it may have on her.
You should decide this on your own. It's a fairly big step to suddenly put yourself together again after this long. Any turmoil (and I think OM contact which undoubtedly will occur would probably create turmoil), and she could be out the door again. That doesn't mean you can't try it and see if you can work through this, if you feel emotionally prepared for continued infidelity, lies, and trust issues. And it's possible to be prepared, if you are of the mind that you will be fine if she leaves again. You are prepared to ask her to go if she cheats on you. But, if you aren't ready to share her, and you aren't ready for her lies and double standards, then I'd suggest drawing a line in the sand. I get the sense that you doing the LRT (and maybe the dating) is what brought her around...but that she isn't completely convinced that she should have opened her mouth and suggested getting back together. Would it be okay by you if she left again? If so, ignore the OM, act as if this isn't happening, and give it a chance. Otherwise, I'd call her on it. Do you know for sure that she's doing the vacation with OM?
In the end, it's not the years in your life that count. It's the life in your years. Abraham Lincoln
It is hard to fail, but it is worse never to have tried to succeed. Theodore Roosevelt
