Her husband, Cristina's father, died when Cristina was still young, leaving her a widow to raise their daughter. They had a family house in San Miguel de Allende, but they also lived at the Institute, which was run by her brother, Tomas.
In December 2007, when the Clave called for Shadowhunters around the world to evacuate the Institutes and retreat to Alicante in light of Sebastian Morgenstern's attacks, Tomas was convinced that Idris would not be safe and insisted that she and Cristina stay in hiding in their house. Tomas himself went, however, and participated in the war. Tomas died during the war, and she replaced him as the head of the Institute.
When the Cohort and its leader, Horace Dearborn, began to gain power and control over the Clave in 2012, Carmen openly stood against him. When battle broke out after their lies were exposed at the parley, she coordinated with Patrick Penhallow and the Silent Brothers to ensure the safety of those inside the city. Rumor said that she climbed up a wall to throw spears at the Unseelie redcaps, and that she punched Lazlo Balogh.
Shortly after the battle, Cristina told her about her relationship with Mark Blackthorn and the new Unseelie King Kieran. Carmen supported her as long as she was happy and said that it was no surprise that "it took two men to fill Diego's shoes."
- Lady Midnight (first mention)
- Lord of Shadows (mentioned only)
- Queen of Air and Darkness (first appearance)
- In early copies of Queen of Air and Darkness, Carmen's surname was mistakenly stated to be "Delgado Mendoza." This mistake was corrected in later editions.