Lawyers for Melissa Todorovic had argued it would be in her best interest to let her remain at the youth facility, where she is serving her first-degree murder sentence for the New Year's Day stabbing of 14-year-old Stefanie Rengel four years ago.
In his decision, reached in less than two hours, Ontario Superior Court Justice Ian Nordheimer rejected defence claims that her exemplary inmate behaviour showed Todorovic had reformed.
"Her faultless conduct while in custody mirrors her conduct at the time of her offence," Nordheimer said. "The concerns remain the same."
Dressed in a lilac hoodie, her long brown hair in a ponytail, Todorovic remained impassive throughout the proceedings, but flushed and seemed close to tears after the decision came down and she was led handcuffed from court.
Todorovic, described as a model daughter and top student, was 15 years old when she finally persuaded her boyfriend David Bagshaw, then 17, to kill Rengel, a girl she had never met but considered a rival anyway.
Evidence was Todorovic goaded Bagshaw for months and used sexual blackmail to get him to commit the murder in east-end Toronto.
Both were convicted of first-degree murder and sentenced as adults.
Under the Youth Criminal Justice Act, transfer to an adult facility is mandatory when a young offender turns 20.
Todorovic had wanted to stay at the Roy McMurtry Youth Centre in Brampton, Ont., where she is the oldest female inmate, while she appeals her conviction and sentence.
Defence lawyer Brian Snell argued that staying put would allow her to get started on a biology course through an Alberta-based distance-learning university.
He maintained she would not be able to do so if moved to the overcrowded Grand Valley Institution for Women in Kitchener, Ont.
"How long can this go on?" Nordheimer asked at one point. "Are you just postponing the inevitable?"
Defence witness Vanessa Thibideau, a case worker at the youth centre, described Todorovic as a model inmate, who finished high school in custody as an A student.
An always upbeat Todorovic was a positive role model for other inmates, participated in all programming and even initiated programs to help others, court heard.
"She is always willing to be helpful," Thibideau testified. "There is a calmness to her. She calms others."
But Crown lawyer Robin Flumerfelt called Todorovic's good behaviour "superficial trappings."
He called her a unique offender with "lethal" issues that are "hard to pin down." He called her manipulative, remorseless, having a "striking" lack of empathy and a "frightening" character flaw.
Todorovic has shown no insight into her offence, has not been diagnosed, and has refused treatment, Flumerfelt told Nordheimer.
"Until that's done, she has not embarked on any meaningful rehabilitation," Flumerfelt said. "She is the person she was then."
Nordheimer, who sentenced her in July 2009, rejected defence arguments that agreeing to treatment would be tantamount to an admission of guilt before her appeal is decided.
Todorovic was never openly hostile or anti-social, the judge noted.
However, she was someone who "conceives of an evil act" and then orchestrates others to carry it out, he said.
Incarceration in an adult facility would be in her best interest because it would offer her more age-appropriate programming and be safer for the young inmates she now has around her, the judge said.
Rengel's mother and other family members left court without commenting.