When Ballard entered Starfleet Academy, she became close friends with Harry Kim, who lived across the hall in their student dorm. She taught him to ice skate, despite his dislike for cold weather. During her Academy years, she never knew that Harry had a crush on her, and that being in the same classes as him was not a coincidence. Her favorite things to eat were peanut butter and jelly sandwiches; during dinner with Captain Kathryn Janeway she mentioned that she used to live on them during her Academy years. Her sloppiness sometimes caused Kim to ask for a baryon sweep of his room.
In 2371, Ballard graduated from Starfleet Academy as an Ensign, and was posted to the newly commissioned USS Voyager, under the command of Captain Janeway. There, she was reunited with Harry Kim. Her primary post was in main engineering.
In 2374, Harry and Lyndsay were assigned to an away mission on a Class-M planet in the Vyntadi Expanse to investigate readings of dilithium ore. However, it was a trap by a Hirogen hunting party, who had reconfigured a power cell to give a false dilithium signal. During their retreat to the shuttle, Ballard was hit by a neural disruptor and died on the way back to Voyager. Harry Kim gave the eulogy and she was buried in space.
- See also: Jhet'leya.
Unknown to the Voyager crew, Ballard's body was recovered by the Kobali, who re-animated her as one of their own, named Jhet'leya. In 2376, she returned to Voyager and attempted to resume her life as Ballard. However, she discovered after a short time that her mind and body were no longer Human. During her time away, she made a list of the things she wanted to do if she ever returned to Voyager. Eating Jibelian berry salad was #6, dazzling B'Elanna Torres was #16, hearing Harry play his music was #26, showing up for duty shifts on time was #27 and making Tuvok laugh was #32.
Ballard's favorite saying came from an old Klingon battle cry, "Own the day." She believed in attacking each day and possessing it. According to Kim, that was what made her so much fun to be around.
She eventually returned to the Kobali when Voyager was being attacked by them, demanding she return. She came to realize that she didn't belong on Voyager anymore, and made the decision herself to go back. (VOY: "Ashes to Ashes")