In 2147, she joined the MACOs (Military Assault Command Operations). Among her assignments were several small engagements while patrolling border and colony worlds, and a six month tour stationed at the Janus Loop.
She held the rank of Corporal in 2153, when the Xindi attacked Earth. Guitierrez had relatives in the state of Florida killed in that attack. Guitierrez was then assigned to the MACO squadron attached to the Starship Enterprise, under Major Joss Hayes.
During the Xindi mission, Guitierrez became romantically involved with Sergeant Nelson Kemper. Though she had believed she was unable to conceive children, she found herself pregnant seven weeks after the beginning of her relationship.
Fearing possible repercussions to both her career and Kemper's, she kept her pregnancy secret, and briefly considered having it terminated. During this time, Guitierrez went on a recon mission with Corporal Hideaki Chang and Ensign Travis Mayweather that turned into a mission to destroy a Xindi refueling and mining depot. During the mission, Private Colin Eby sacrificed his life for Guitierrez and her unborn baby. After this, Guitierrez decided to keep her baby, and eventually gave birth to their daughter, whom they named Elena. Nelson and Selma then resigned from the MACO service to be a proper family.
Guitierrez was apparently among the few who knew the truth of the fate of Commander Charles Tucker III, who remained close to her family for many years. (ENT novels: Last Full Measure, The Good That Men Do)
In 2155, Guitierrez and Kemper were both bothered by Earth's losses in the Earth-Romulan War and decided that one of them must rejoin the MACOs while the other cared for Elena. In the end, they decided on flipping a dollar coin that Kemper had. Guitierrez won the coin toss and returned to active duty in the MACO.
In April 2, 2156 she was deployed from the USS Dykstra to Berengaria VII, where she fought in the Second Battle of Berengaria, during which she helped Colin Idaho survive his first battle with the MACOs despite that their entire unite was wiped out. (ENT novel: Beneath the Raptor's Wing)
In 2157, Guitierrez was serving as a Sergeant aboard the Enterprise when she led a squad of MACOs to the surface of Galorndon Core in order to recover scientists Hans Ruden and Emily Jensen. During the battle Guitierrez was wounded severely and only survived because Private Owen Salazar-Tucker saved her by carrying her to the squad's shuttlepod. (ENT - The Romulan War novel: To Brave the Storm)
|Enterprise (NX-01) personnel|
|Earth Starfleet personnel||Almack • J. Anderson • Ansara • J.B. Archer • Baird • L. Bilani • Billy • Bishop • K. Borovsky • M. Burch • Burrows • Camacho • Carstairs • R. Chandra • Cole • Cook • Cravens • E. Cutler • Daniels • Diaz • Dickison • Duel • J. Edwards • M. Fincke • Foster • A. Gaeta • Garver • A. Hart • Hess • J. Horn • Hutchison • Kelby • J. Kelly • Kimball • Ko • J. Lee • E. Leydon • F. Marcel • T. Mayweather • M. McCall • Meir • Nguyen • E. Novakovich • D. O'Neill • Perkins • Phlox • Pointer • M. Reed • A. Rhodes • K. Riley • M. Rostov • K.P. Ryan • A. al Saed • Salvatore • Santini • H. Sato • Stepanczyk • J. Taylor • T'Pol • Tom • C. Tucker III • D. Walsh • Williams • Zabel|
|MACO contingent||D. Chang • A. Cole • Costa • C. Eby • S. Guitierrez • J. Hayes • M. Kelly • N. Kemper • T. Kimura • D. McCammon • J. McKenzie • S. Money • Ogilvy • O'Malley • M. Peruzzi • O. Salazar-Tucker • W. Woods|