Red, are you thinking of the poster who's husband had a baby with another woman?
Whilst this post is similar, i dont think it's the same person, though I could be wrong!
Samsworld- I'm gonna reiterate what everyone else has already said. I can't believe you've seriously thought of doing this to this woman, and she is a woman ,not a slip of a girl! And more importantly why you'd do this to her parents- what on earth have they ever done to you?
If my daughter at 28 was sleeping with a married man, whilst i wouldn't be impressed, it would be her life and not for me to lay the law down. Your husband is the one who commited adultery, not her, she's free to sleep with who she likes.