The answer to the question “Why did Herb and Judith break up in the TV sitcom Two and a half men?” is because she caught Herb cheating on her with his receptionist. However, this specific scene of her catching Herb cheating was not seen in the series. Judith Melnick did not appear on the season 10 of the series and it was only in the episode Run, Steven Staven! Run! Did Herb reveal why she was no longer present – thus, revealing about the infidelity and the subsequent end of their relationship.
She reappeared again on one episode of Season 11, but she only talked to Alan, her first husband. She reappeared again on one episode of Season 11 and it marked her last appearance on the show.