Dude, that stinks.
I'd drop her like she was hot. Adultery isn't even cool with Jehovah.
Depending on how vengeful you are, you could cause her a bunch of trouble with the Elders and ruin her position in Jehovah's organization which she covets so much.
Sorry to hear it, I was in a relationship where I assumed there was cheating, I didn't have substantial evidence, and I hadn't been involved as long as you have, married, etc.