How do I confront her about the last 2 nights of sex chats WITHOUT giving away exactly how I know?

All I could say is that when she used to chat on facebook, shes type a bit for a message, and do something else. Now, I can hear her typing FURIOUSLY at night, going back and forth. You can almost tell when she's getting more and more excited.

I'm scared to give away the one true ace in the hole that I have.

What I could do is tell her the wireless router fried, but block all her network traffic using the admin panel of the router. Then she couldn't use her laptop to do this.

Me - 32
Her -30
Married - 7 Years
Together - 9 Years
No Kids
05/21 - Bomb
6/8 - Exposed
7/9 - Re-Exposed
06/11 - She Filed