Before her promotion to the rank of captain, Hernandez was romantically involved with fellow Starfleet officer Jonathan Archer. However, when Archer was promoted, becoming Hernandez's superior officer, he broke off their relationship. (ENT: "Home")
Hernandez's last assignment prior to taking command of Columbia was on the Republic, under Captain Jennings. When she left the ship, Jennings told her that she could have anything that she wanted. Hernandez ultimately chose to take his chef. (ENT: "Affliction")
Hernandez's promotion to captain was in 2154. She was then assigned, along with several other officers, to audit Archer's debriefing subsequent to the Enterprise NX-01's return from the Delphic Expanse. After Archer was ordered to take some time off by Admiral Forrest, Hernandez joined Archer as he went rock climbing. Although Archer was initially reluctant to accept Hernandez's company, as he viewed her as an uncomfortable reminder of the personal sacrifices he had made during his mission to save Earth from the Xindi, Hernandez was successful in assisting Archer in reconnecting with his Humanity, and briefly rekindled their intimate relationship. (ENT: "Home")
Although Columbia was initially scheduled to launch in June of 2154, engine difficulties prevented the ship's departure from spacedock until November of that year. During that time, Hernandez twice unsuccessfully attempted to recruit Commander Charles Tucker, chief engineer of Enterprise, to her crew. Ultimately, Tucker chose to accept the transfer for personal reasons, and was able to accomplish modifications allowing Columbia to launch. Shortly afterwards, Hernandez was contacted by Captain Archer, who was requesting Tucker's assistance in repairing Enterprise's warp drive, which had been sabotaged by Klingons. After the successful repairs to Enterprise's engines, Hernandez and her crew joined Enterprise in a dangerous mission into Klingon space to rescue their chief medical officer, Doctor Phlox, and in resolving a crisis involving a virus spreading throughout the Klingon Empire. After the resolution of the crisis, Hernandez granted Archer's request to keep Tucker aboard Enterprise to assist with repairs. Eventually, Tucker asked Hernandez for a permanent transfer back to Enterprise, a request which Hernandez granted. (ENT: "The Expanse", "United", "The Aenar", "Affliction", "Divergence", and more)
In the script for "Home", Erika Hernandez is characterized as "late thirties," during the events of that story. The script goes on to say, "She’s of slight build and carries herself with an air of confidence." Hernandez was played by Ada Maris.
Hernandez makes appearances in several novels, including Kobayashi Maru and the Star Trek: Destiny trilogy. In the aforementioned trilogy, Captain Hernandez and her crew went to an uncharted system, after narrowly escaping a Romulan attack in Kobayashi Maru. There, they met the reclusive, technologically-advanced Caeliar. Years passed until Hernandez was the only one left alive. But a Caeliar whom Hernandez and her crew first met, named Inyx, used his technology to infuse cellular "catoms" (nanites) into her, making her near immortal. She was partially responsible for the creation of the Borg, as three of her crew members were the first Borg, two of whom were the first surviving Borg, and were accidentally created with Caeliar technology.