A lot of us LBS has gone through the I love you but not in love with you bs.
It's part of the delusion, the good news is that people can snap out of it, but it can be a long hard road.
It's possible, even probable actually that there is an OM. Your W is behaving like the typical "grass is greener on the other side" mode. I don't think you're competing with a vision of life by herself.
No point asking. Find out if you have to, and work on yourself in any case. She's lost respect for you.
For what it's worth, I would have literally bet my life my W wasn't in an A till I found indisputable proof. And you would not have believed how sincere and convincing she, like any WAS, can be when they deny having "a special friend".
Me 42 W 39 Married: 11 Jan 1998, T: Since 1992 First Bomb: Sep 2007 Confirmed A/OM: 4 Nov 2007 Kids: D10, S5 Reconciled and together again after (alot of) time and heartbreak. 3rd kid, S, born 2 Jan 2010.