The young woman who orchestrated the stabbing death of Toronto teen Stefanie Rengel must move to a federal adult prison, a judge ruled on Thursday.

Melissa Todorovic had been seeking an order that would allow her to stay at the Roy McMurtry Youth Centre in Brampton, Ont. where documents show a walking club and a cooking program are among her activities.

CTV Toronto's John Musselman reported that a judge dismissed Todorovic's application, ruling that she must transfer to Kitchener's Grand Valley Institution for Women.

It's been almost three years since Todorovic convinced her then-boyfriend David Bagshaw to lure the 14-year-old Rengel out of her east-end home, where he then stabbed her six times and left her to die in a snowbank.

Bagshaw, then 17, and Todorovic, then 15, were convicted as adults for first-degree murder. Both received life sentences.

Todorovic is due to turn 20 next month, a milestone that comes with the transfer to a federal penitentiary in Kitchener, Ont.

In a statement released before the judge's ruling, her lawyer Brian Snell said Todorovic should be allowed to stay at the centre so she can continue her rehabilitation without interruption.

"It is respectfully submitted that it would be in her best interests to remain where she is pending the determination of the appeal," he wrote.

Since her 2009 conviction, Todorovic has graduated from high school with straight As and is working towards finishing a science course.

Staff reports from Roy McMurtry Youth Centre describe Todorovic as a busy inmate who maintains a "platinum level" in programs at the centre.

The reports contrast against Ontario Justice Ian Nordheimer's description of Todorovic as a "puppet master" who jealously ordered the death of Rengel, a perceived romantic rival.