Dolores Mattone is an unseen hidden villainess mentioned in Blue Bloods' fifth season opener, "Partners" (airdate September 26, 2014). She is a group secretary for the DEA.
In the episode, a truck full of drugs confiscated by the DEA was stolen by members of the Mara Noche gang, who engaged in a shootout with detectives Danny Reagan and Maria Baez--the latter of whom was (non-fatally) shot. In addition to taking the drugs, the group shot and killed Agent Ramirez after abducting her, and the investigation revealed a familiar connection: Javi Baez--Maria's brother. During the interrogation, Javi revealed that he had spent three months as a DEA informant reporting on Mara Noche, and he also revealed that the gang received info on the transport from someone inside of DEA.
Danny's search of the DEA mole revealed that only four people knew about Javi being an informant: three agents and Dolores. After it was uncovered that Dolores posted bail for a Mara Noche member a year prior, the group contacted Dolores and informed her that they found the location of the drugs, after which she accepted an order to round up the rest of the officers. Dolores turned heel afterwards by calling gang member Ramon Sanchez and warning him to move the drugs, stating that the NYPD and DEA found out, which officially revealed Dolores as a villainous mole. Following the gang's capture, the evil Dolores ended up arrested (off-screen) for her collusion.