From what your W's friend told you, tat-boy remains just a fantasy. Your W likely pm'd tat-boy on a whim. He may not even know her and who knows, if he has some fanboy page, he probably gets propositions all the time. And further, I'd put guesses that if he's still married to his W, that he remains faithful to his W.
It would be a wonder that your W somehow would rank on his list of trophy's, if he has any. Considering she was at his city and apparently he did not succumb to her charm, then.
Continue to leave it alone, CB. She needs to come to her own realization that he is just a fantasy she is stalking. Or you risk her blaming you for her fantasy not becoming a reality and she will remain stuck.