Cherishher, First of all, I'm so sorry. That's a horrible thing to become aware of.
I don't see that there's much you can do. This is another one of those things you can't control. You cannot control your wife... she is an adult. You can control your own feelings. This is going to be a HUGE test of those jealousy issues. If you can get through this without going crazy jealous, it'll be a huge step.
First of all, I would try to find out if this is really true. I'm assuming there is a chance this may not be true? Or is it 100% certain?
Secondly, try to contact her by e-mail or whatever. Ther emust be someone who will hear from her soon. I really don't think she's going to listen to you if you just tell her what she's doing is wrong or hurtful to her family. It's what she feels - you can't change that. You can try to expose the dangers of getting involved with someone from these boards and tell her about the cases that have already occured (Look up BrandNewDay's post), as a friend. But there is little else you can do. She may be just visiting a friend.
I think you'll just have to wait it out. It's a vacation... she'll come back.
May it be eternal while it lasts.
My sitch
Me: 36
H:34
M: 5 years
Bomb: 03/14/06