She flew to space in September 2024 on Polaris Dawn, a private human spaceflight mission, operated by SpaceX on behalf of Jared Isaacman.

[5][4] In 2015, while at the University of Colorado Boulder, Gillis began an internship at SpaceX, working on human-in-the-loop testing of the Dragon spacecraft before moving full-time to the astronaut training program.

[6] She is a lead space operations engineer at SpaceX, responsible for overseeing the astronaut training program for the company's Crew Dragon vehicles.

[7] In September 2024 Gillis flew on Polaris Dawn, a private spaceflight operated by SpaceX on behalf of Shift4 CEO Jared Isaacman.

[10] Later during the mission, Gillis, a classically trained violinist, played the solo violin part of "Rey's Theme" by John Williams from the 2015 film Star Wars: The Force Awakens to raise money for St. Jude Children's Research Hospital and El Sistema.