The teen, now 17, was found guilty on 27 counts, including procurement for the purpose of prostitution, human trafficking, making child pornography, sexual assault, child luring, uttering threats and unlawful confinement, the Canadian Broadcasting Corp. reported.
"This is the first time in Canada a youth has been convicted of human trafficking, so it's huge," Ottawa police Detective Carolyn Botting said. "It says that despite your age and despite what you are doing you will be treated accordingly."
The girl, whose name wasn't revealed, was acquitted of three charges and two other counts were withdrawn.
Prosecutors said they intend to seek to have her sentenced as an adult after a psychiatric assessment.
Two other teenage girls pleaded guilty in the case last September, the CBC said.