Marayna appeared to be a holodeck character but was the projection of a lonely alien woman who became fixated on Tuvok.
Marayna seemed to be a character in a tropical luau program on Voyager's holodeck. Harry Kim fell for her and asked Tuvok to help him suppress his feelings, but she turned her attention to the Vulcan, who was intrigued by her logic.
In Alter Ego, Marayna was revealed to be the projection of an alien woman living alone on a station inside an inversion nebula, maintaining it so it would not burn out. Isolated and lonely, she took control of Voyager to keep Tuvok near her. Tuvok visited her in person and persuaded her to release the ship.