i should probably head over to the infidelity forum as much as it might turn my stomach...
The difference over on that forum is you would get step-by-step of "how-to"deal with the infidelity in your stitch.
As for my asking if you have solid proof, that is b/c without it then it's just your word against her's. You made need to put those phone records in a safe place. You made need to make notation of very late nights or over-the-top excuses that you find a bit fishy.
Not something one enjoys, but you need to protect yourself. Protect your bank accounts, credit cards, etc. Remember, she's not in her right mind.
It is not about what you feel should work in your M. It is about doing the work that gets the right results. Do what works!