Being a Shadowhunter, Beatriz was placed on the more advanced curriculum stream for Shadowhunters and special cases (such as famed Simon Lewis—a mundane placed on the stream) that their kind consider elite. With fellow students Jon Cartwright and Julie Beauvale, she befriended Simon and his roommate George Lovelace. When Simon and George left the stream, and their little group, because of Jon and Julie's harsh words for Downworlders and mundanes, she was impressed by Simon's decision and asked them both to remain friends with her.
Beatriz was eager for the following day's guest lecturer, who turned out to be Simon's former girlfriend, Isabelle Lightwood. When Isabelle warned anyone off of flirting with Simon, Beatriz, who had been sitting next to him, inched away in fear.
When Isabelle returned to the Academy with her father, Robert Lightwood, Beatriz was among those bothered by the revelation that the current Inquisitor was, in fact, a member of the Circle. In fact, Beatriz was incredibly disturbed by this that even Isabelle earned her ire, though she politely talked with the latter about mutual acquaintances.
However, when Isabelle suggested that the students do something fun yet dangerous and troublesome, Beatriz was quick to go against the idea and did not join the majority of the other students in their rule-breaking trip for 'fun' with Isabelle. When the others had yet to return by five in the morning, she worried that they had gotten in trouble and immediately went to Simon, asking him for help in finding the others. When Simon refused, saying he knew that Isabelle would not let anything happen to them, Beatriz refused to just trust Isabelle and became furious at him.
Beatriz went on to become a tutor and trainer at the New York Institute, under the new heads Clary Fairchild and Jace Herondale. She had evidently gotten over her crush on Simon and was thrilled when Simon announced his engagement to Isabelle. She also helped Clary throw the pair an impromptu engagement party.
In 2012, she attended the war council meeting called by Julian Blackthorn at the Los Angeles Institute. They joined the procession of Shadowhunters at the parley staged by the Cohort. Beatriz was next to Julie when the latter was killed by an arrow intended for Kieran. Beatriz was devastated and was carried out of the battlefield and into Alicante in tears.
In the weeks after the battle, Beatriz helped set up the new Shadowhunter Academy in New York along with Simon, Marisol Garza, and Luke Garroway. She then attended Alec and Magnus's wedding in Los Angeles. She still wore white, symbolizing that she was mourning Julie's death, along with Marisol, who was also still in mourning over their classmate and Marisol's boyfriend Jon.
Beatriz has brown skin, black hair, and, according to Simon, a warm smile.
- Despite being raised a Shadowhunter, Beatriz was not raised in Idris and has some idea about mundane culture; she is aware of 'Brangelina'.
- Beatriz is distantly related to Cristina Rosales. Beatriz's mother is a Mendoza, as was Cristina's father.