|“||Hey, do you think you'll ever catch Joe's partner?||”|
"I loved him. That's why I did those things. After a while, he didn't even have to ask me to do it. I just did."
Daria was originally a medical student at Cornell University who enjoyed a close relationship with her sister Ellen. She also worked part-time as a diner waitress. While walking to the diner with Ellen in March 2012, she encountered Joe Bachner, who flirted with her. Later that day, he managed to get her into his car. When Daria woke up after being suddenly rendered unconscious, she found herself tied up in Joe's house; he then held her captive, repeatedly raping and torturing her. Eventually, Daria submitted to the torture, developing Stockholm syndrome and gradually falling in love with Joe. Once she was completely submissive towards him, she acted as a partner for his crimes, cleaning up his tool-shed and helping him dispose the bodies of other victims. At some point in 2013, a woman named Carrie, Joe's latest captive, managed to smuggle the key to the shed one night and convinced Daria to help her escape. They broke out, but when an awakened Joe fired several shots from a rifle, wounding Carrie, Daria panicked and left her behind, running through the forest and out into the road, where she was hit by a passing truck.
Rescued (likely by the truck driver), Daria later woke up in the hospital, having been rendered in a dissociative state due to the trauma and the accident. She alternated between hysterically begging for Carrie's forgiveness and screaming about "them", but nonetheless gave the BAU (who had been called in after three of Joe's victims were found) key clues about the unsub. Her mind having been broken, she convinced herself that Joe's partner was one of his poker buddies, a man named Coby Peters, who coincidentally had medical training; this caused the BAU to briefly suspect him of being the actual accomplice to the murders. However, when they quickly realized he wasn't the partner, he provided them with Joe's location, which enabled them to arrest Joe and rescue Carrie, as well as a man he abducted after Daria escaped. During another interview, Morgan noticed that Daria was constantly making things around her neat, a sign of the OCD they had profiled the submissive partner as having. He made her divulge the location of an icepick, and then confronted her with the truth: she was the other partner. Unable to accept this, Daria started screaming and apparently descended further into a dissociative state, ending up in the Maynard Grove Mental Institution for a year.
The Edge of Winter
In the episode, Morgan visits her again to prepare her for Joe's trial as a sympathetic witness. After going over the events of last year, he makes her face her role as Joe's accomplice. He assumes that Joe had coerced her, but she calmly reveals that she did her part willingly, having fallen in love with him. Disappointed, Morgan sadly tells Ellen that Daria will be staying in the hospital for the rest of her life lest she faces jail time. After taking her medication, she slips back into her delusional state and innocently asks if Morgan will ever find Joe's partner. He replies with "I'm not sure, but we're still looking". She wishes him good luck and he says goodbye.
Under Joe's influence, Daria would inflict at least some of the torture on his victims for him. She would do so by stabbing them 28 times with an icepick under his orders. The wounds were always positioned in seven groups of four each due to her OCD. Daria would then help Joe dispose of the bodies afterwards.