I don't want to throw this in your face but in light of your impreesions of my marriage I feel I have to. I have never cheated on my wife. She has never cheated on me. That alone puts my marriage squarely in a different zone then yours.
To be clear, I'm very happily remarried. The situation described above is with my ex-husband.
No one has accused you of cheating Paulination. I only shared my story to shed light on why/how I can connect with how your wife feels. What I see you doing is dismissing her, just like I was dismissed in that marriage, and it led me to do the things I did as a result. While you may not be doing it now, it went on long enough for her to be trashing you behind your back and doing things like changing her passwords to insulting remarks aimed at you.
You're sure she's not cheating now and thats fine. What you refuse to acknowledge is that her actions and behaviors are setting up a scenario. Keep watching, and don't let your guard down. As long as this 'friend' and she are talking about you, you can't afford to.