Assume Bill has met Robin on the Internet.  He portrays himself as a single doctor.  After the tenth date Robin and Bill have sexual relations.  Can Bill’s wife sue Robin?  Absolutely!

. . .  Bill has signed a separation agreement that says he and his wife can live as if unmarried in all respects.  It is signed, notarized, and drafted by attorneys.  It doesn’t include a third party waiver.  Bill tells Robin they have been legally separated.  She is skittish about the fact that he is separated until she reads the language from his separation agreement that says they can live as if they were not married.  And it is, after all, notarized.  Feeling assured, they proceed to have a romantic relationship.  Can Bill’s wife sue Robin?  Absolutely!