Sito first appeared in the fifth season episode "The First Duty" as a Starfleet Academy cadet. She was a close friend of former Enterprise crewman Wesley Crusher and both were members of the Academy's elite flight team Nova Squadron. When the squadron was indicted for the performance of an illegal flight maneuver that resulted in the death of one of the squad members, Sito took part in attempting to cover it up, but Crusher came forward and confessed the truth. Because of this, Sito's tenure at Starfleet Academy was shaky and she was shunned by the other cadets, but two years later she graduated from the Academy and gained a position aboard the Enterprise.
In the seventh season episode "Lower Decks", Sito had achieved the rank of Ensign and was assigned to Enterprise security under Lt. Worf. She became close friends with a group of other young officers who readily accepted her despite her transgressions while at the Academy.
Sito would be called upon by Captain Jean-Luc Picard for an important mission into Cardassian space, accompanying a Cardassian officer who had become disgruntled with his people's military and sought to put an end to the needless border disputes between the Federation and Cardassia. Sito accompanied the Cardassian under the guise of an abused Bajoran captive, an efficient cover given the decades of animosity between the Cardassian and Bajoran races. The pair crossed into Cardassian space in an Enterprise shuttle, claiming it was stolen, and Sito would be allowed to "escape captivity" as the Cardassian returned to his people.
Not all went as planned. The Enterprise was supposed to rendezvous with Sito's escape pod but she never returned. Debris consistent with a Starfleet escape pod was later discovered, indicating that Sito was killed by a Cardassian border patrol on her way back to the Enterprise. Captain Picard later made an announcement to the crew regarding Sito's loss.