Selok
Subcommander Selok was an officer in the Romulan fleet, who served the Romulan Star Empire as a spy. She entered the United Federation of Planets posing as a Vulcan Ambassador T'Pel. By 2367 she managed to establish a renowned name in her service.
When her espionage service was concluded, the Romulans arranged her accidental "death" while being transported from USS Enterprise-D to the warbird IRW Devoras so that she could return to the Romulan fleet. (TNG: "Data's Day")
Selok/T'Pel was played by actress Sierra Pecheur.