Barbara Keyes (Rebecca Naomi Jones) is a villainess from "Manhattan Queens," episode 4.14 of Blue Bloods (airdate February 21, 2014). She was the girlfriend of a drug dealer who was fatally gunned down two years prior to the episode's events.
Timothy Cooper, who went to the dealer looking to purchase marijuana for his dying mother, Doris Cooper, was accused and convicted of the murder, with both Barbara and Marius Pierre identifying Timothy as the shooter. A desperate Doris abducted Erin Reagan in the episode's opening and pleaded with her to exonerate her son, and it led to Erin visiting Barbara while she was leaving her apartment. Barbara responded rudely to Erin's requests for an interview, adding that she already answered questions regarding the shooting before walking off.
As Barbara walked off, Erin commented on her jacket, which ended up leading to a number of reveals. First, it was uncovered that Barbara's jacket cost $3000, and after Erin was informed that very little cash was found at the murder scene, it led to the conclusion that Barbara had taken most of the money for herself and spent some when she became impatient. In addition, it was revealed that Barbara was convicted for a small possession of narcotics, along with Marius, which contradicted Barbara's claim in her testimony that she and Marius never knew each other. This resulted in the belief that the pair set up Timothy, and a recording confirmed the reveal.
As it turned out, Marius killed the drug dealer, after which he and Barbara stole most of his money and set up Timothy in the murder. A recording played by Erin revealed a conversation between the conspirators that took place following Barbara's meeting with Erin, with the evil Barbara responding to Marius' questions regarding buying her new coat by stating that she needed one, after which Marius stated that they weren't supposed to spend the money until after the trial. After the recording was played, Barbara was arrested (off-screen) as an accessory to her boyfriend's murder, as well as conspiracy and perjury.