"Let me think about this one. I do think that what I will say (and this will be in person, because I want to look her square in the eyes) is "And I do intend to protect my interests here. I don't mind people flattering you, and I'm sure it makes you feel good, but if it goes beyond that, I will get involved, and it will be immediate and it will be forceful. You asked me for honesty, so there's brutal honesty for you."
Choc, this seems perfect. I would NOT bring up her EA. IF it exists, it is not the problem in your M, but a symptom. And, trust me, the people seriously involved in EAs or PAs do NOT respond to their spouses in the way your W has responded to you.
The whole exchange is INCREDIBLY powerful and VERY loving on both sides.
And, your email was perfect. I think emailing is a TERRIFIC way for the two of you to communicate. IT WORKS. DO WHAT WORKS. It allows you both to drop your defenses, really hear each other because you can reread the emails, and to say what you really want to say rather than spouting knee jerk reactions from bad ingrained patterns.
I have to tell you, the strong and direct thing looks REALLY great on you. Keep it up.
Also, if you haven't read DR, it is time to do so, or time to reread it. You might want to start participating in some of the other forums as well, perhaps even Piecing. You have a much stronger grounding and a LOT more buy in from your W on growing a wonderful M together than many people who find themselves there.
I am so happy for you!!! No matter how this turns out, your life will no be so much better. You are like the Grinch, whose heart was two sizes to small but has now opened up to have a heart to be admired by all.