I think available to talk about the mess she made is more the way I would describe it. The OM helped her make the mess unfortunately.
What I was taught to say and do was to say to my wife "This is your mess; you get to clean it up." Not to take any ownership of her poor decisions, nor to instruct her on what to do (which she would only see as "controlling" anyway.
A betrayed spouse shouldn't get involved with helping solve a wayward spouse's problems that are directly a result of their infidelity.
I guess we'll just have to disagree about this one, Michael.
"Still at the end of every hard-earned day, people find some reason to believe" -- Bruce Springsteen