Radio-Canada reported Thursday that Sabrine Djermane's sister allegedly heard her say that if ''we can't go over there, we'll do it here.''
Djermane and El Mahdi Jamali were arrested by the RCMP as a preventive measure on April 14.
They were arraigned this week on charges of attempting to leave Canada to commit an terrorist act abroad; possession of an explosive substance; facilitating a terrorist act; and committing an act under the direction or for the profit of a terrorist organization.
Both pleaded not guilty.
Radio-Canada reported sources as saying police acted quickly after being tipped off to the alleged plot by Djermane's relative.
The broadcaster says police also searched the home of Jamali's parents and found materials that could be used to make a pressure-cooker bomb similar to the one used to kill people at the Boston Marathon in 2013.
Djermane and Jamali's case resumes in court Friday.