"He's gonna hurt me like they all did!"
Juliet's father was Morris Monroe, a serial rapist whose favorite target was her. The sexual abuse eventually triggered a fear of men by her, but also an apparent hybristophilia, or an attraction to violent men. As a result, Juliet kept visiting her father when he was caught and imprisoned for his crimes. In prison, she met Robert Burke, another serial rapist, and fell in love with him. The two formed an intimate relationship that eventually culminated in Juliet's pregnancy by Robert when he was released from prison. In 2000, Robert started abducting, raping, and killing girls, with Juliet assisting him. In 2010, when police began to close in on Robert, he realized it and, not wanting to go back to prison, committed suicide at a warehouse he purchased.
...A Thousand WordsEdit
The day after the suicide, Juliet receives Robert's suicide note and final instructions to kill Rebecca Daniels, the latest victim, who she later blames for his death. When Reid reads the journals, he finds a sentence revealing that Robert has a partner. Later, when Reid and JJ are examining a blank spot on Robert's body with a UV light, they find an "invisible" tattoo of a fetus, indicating the partner is a woman with whom he was having a baby. In the meantime, Juliet goes into labor at her house and Rebecca is forced to deliver it. When the child turns out to be a boy, Juliet becomes terrified of it and backs away, saying that it would hurt her like the other men in her life had done. Before dying, possibly from blood loss, she states that she was sure she was having a girl. In the meantime, the BAU track down her home and are able to save Rebecca as well as the baby, who was most likely adopted afterwards.
It is never specified how exactly Juliet assisted Robert in holding his victims captive. However, it was suggested that she took part in some of the abuse Robert inflicted on them. In ...A Thousand Words, she was seen abusing Rebecca by knocking her down to the floor while collared and then pressing down on the chain, effectively strangling her.
No specific profile of Juliet was made by the BAU, who were more focused on deducing Robert's motivations for his murders. However, she is apparently a hybristophile who is attracted to violent men, which stemmed from the sexual abuse she suffered at the hands of her father.