Marie and Paul Napoli are embroiled in a court battle with lawyer Vanessa Dennis. Photo / AP
In her complaint, Dennis, 33, said that Napoli, 47, waged an unremitting campaign against her, her family and her friends with messages denouncing and threatening her sent via email, Facebook and other social media sites.
The court papers feature graphic sexual details and insults contained in emails from the two women.
Dennis said Napoli harassed her even after she moved to a new job in Texas by sending Christmas cards to the wives of her new bosses describing Dennis as a "sex addict" and warning: "If I were you, I would not let her near my husband."
The Napolis, who met at law school in New York, are reported to have briefly split but are now back together, with expensive homes in Manhattan, Long Island and the Hamptons.
Napoli, 46, told the New York Post he supported his wife for "confronting a person that there was an affair with". He denied she had anything to do with the disappearance of Dennis' cat.
Marie Napoli has filed court papers claiming she suffered after Dennis allegedly persuaded her husband to have sex during a business trip.
In a separate case, Paul Napoli and Marc Bern, another founding partner, are engaged in an ugly battle for control of the company.
What is certain is that the future of a law firm renowned for its ability to sue others is now in the hands of the lawyers.