It is implied that Elena comes from a Hispanic immigrant family as she speaks with an accent and is fluent in Spanish. When she first joined the team, she was already separated from her ex-boyfriend Carlos Aguilar and raises their daughter Sofia on her own. In the episode "Honor Bound", she reveals that she spent much of her adolescence rebelling against her traditionalist family, which provides some useful insight into the case.
Elena joined the team during the third episode of Season 4 as Jack's team was stretched to its limit. She was previously an experienced NYPD officer prior to joining the FBI. Her working relationship with supervisor Jack Malone starts off rather coldly as she had been hoping to be transferred to White Collar Crimes but was sent to Missing Persons instead. She soon catches the attention of Danny Taylor, who happened to be acquainted with her estranged ex-boyfriend Carlos. While in the midst of an ongoing custody battle for their daughter Sofia, Elena is kidnapped by Carlos and was later rescued. She continued dating Danny after the incident. They marry at the end of Season 7.