She was with Star Trek from the beginning, playing the first officer of the Enterprise, the otherwise nameless Number One, in the original pilot episode. She was a semi-regular on the series in two roles, as Nurse Christine Chapel and as the voice of the ship's computer.
However, it was on Star Trek: The Next Generation that she came into her own as the "Auntie Mame of the galaxy," Lawaxana Troi, mother of regular character Deanna Troi. She also played the role on Deep Space Nine. On all the Trek series, she continued to voice various Federation computers to the very end (to date) of Star Trek on broadcast television, the finale of Enterprise in 2005.
Her final role in Star Trek, completed before her death, will be in the original series-reboot feature film, coming out next May, again as the Enterprise computer. The final Trek performance released during her lifetime was the Star Trek New Voyages episode "World Enough and Time," reprising the role of the original NCC-1701 Enterprise's computer.
She married Star Trek creator Gene Roddenberry shortly after the end of the original series in 1969. Following his death in 1991, she was instrumental in bringing two of his unmade projects, Earth: Final Conflict and Andromeda, to television, where they enjoyed long runs.
I only ever saw her once in person, at a convention in Chicago in 1986. She happily delivered the news of the very positive preview figures for the then-upcoming Star Trek IV: The Voyage Home, and the first news about what became Star Trek: The Next Generation. I'll never forget how she raised goosebumps reading the Federation President's speech from Voyage Home, recounting the disaster that had befallen Earth and urging all listeners to avoid the planet "at all cost."