She was a member of the terrorist group Open Sky, a group of self-proclaimed patriots. In 2373, She and her brother extracted paralithium from their own freighter's hull and synthesized it to trilithium in order to conceive an explosive device.
This device would later be used in the bombing of the Laktivia recreation facility on Akritiri. The bombing cost the lives of forty-seven Akritirian and landed two Humans, Harry Kim and Tom Paris, that were visiting from the USS Voyager were wrongly accused and sentenced to the Akritirian maximum security detention facility.
Piri was rescued from that same detention center by Vel, who was also an Open Sky member, after he led Voyager to the prison where she was also being detained. Eventually Captain Kathryn Janeway let the duo go without facing the Akritirian authorities. (VOY episode: "The Chute")