Yes, think of how humiliating it will be.
Oh wait, I think she's been humiliated already. So don't think she's supposed to take this lying down and suffer in silence.
Depends on what she does.
Email the boss ? Why ? It's none of his business.
Email the husband and family ? Why ? To bust up the other family as well as her own ? Now that's mature.
Email the employer and clients ? Why ? It's none of their business either.
And what's with the "homebreaker" bullsh!t. It's takes two you know (or did last time I did it).
No one said suffer in silence and by all means get square. Just be mature about it. The previous suggestions reek of teenage girl behaviour.
It says in the first post that the husband of the woman involved has already left her and that she got fired from her job, so emailing bosses and husbands and all that would be fruitless.
As for the OP keeping out of it - I reckon that 9 times out of 10, when a person says 'my friend', they're actually talking about themselves, so I wouldn't be surprised if the OP was the wife in question.
However, I still say ditch him. You'll never trust him 100% again.