She will come home, or I'll find it in my own mind

[Nomopo]

But how do you go about finding out from her what she is getting out of this, without a) asking, and b) snooping?

The only route I come up with is listen intently to what she says I do wrong, I imaging the opposite of that is what he does right, so I have to do the opposite don't I?

I think this is about right. Keep thinking on it. Things wil come to you. Realizations, etc. Think about what her complaints are about you and the M. Chances are, OM is filling some of those voids. He probably makes her feel great about herself.

Do you know OM? I knew my W's OM - he was a friend of hers from work, and we interacted with him at times. He's been to our house, played with our kids, etc. W told me stuff about their interactions (pre-discovery). I found more by snooping (pre-DR). So I had some insights into their R.

Hope it helps,
Nomo

PS - don't over do the PLL stuff. If it's too thick, it could be pressure that will drive her away and also be viewed as not sincere. Take it slowly. (maybe not a gift everytime she comes over. How often is that?