She could write NY and ask what they think about it and how her Christian friends (non jw's) think he is being unfaithful. It doesn't matter that the wife is not a jw or even an apostate, he is giving the borg a bad name and you know how much they care about that!
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Unfortunately, anymore it is not what's right that prevails in the cong., but who you are. This man being a JW will garner him a lot of protection/leniency over his "apostate" wife.
I've seen this kind of thing first hand. Elders will either handle a situation correctly, seeing an emotional affair for what it is-dangerous, or they'll dismiss it as "trivial" if they happen to like the person carrying on the affair more than they like their spouse/victim. The advice to the victim will likely be to just take it, let your spouse do what they want.
The hoops Elders will jump through to defend the wrongdoer can be quite astonishing.