This Human female was a member of the Soaring Hawkbat Clan. The clan was stationed a the Jedi chapter house on Bogden 3. They were awaiting transport back to the Coruscant Jedi Temple, which had been delayed due to the battle there. When Masters K'Kruhk and Sian Jeisel arrived with their clone troopers, Order 66 was issued. Several of the younglings were killed as Du Mahn defended them. K'Kruhk and Piru ultimately escaped with nine younglings to parts unknown. Two months afterwards, Sidirri was living with the group of younglings in exile under the tutelage of K'Kruhk.
Sidirri was present when Lumbra and his men came to the youngling's camp. When they noticed that the broken ship had a piece that they needed, Lumbra proceeded to take it. As he approached the ship, fellow youngling, Seddwia, jumped at him saying that it was their ship and to leave it alone. Lumbra grabbed Seddwia by the arm and pulled her away, starting a conflict. Chase Piru jumped to her rescue, but was shot and believed dead. When Lumbra realized they were Jedi younglings, they were chained up and on their way to be turned into the Galactic Empire.
The younglings were freed by K'Kruhk who gave in to un-Jedi like behavior briefly. With the help of Chase Piru he shot down Lumbra's men with arrows. Lumbra and his shipmate, Callow, died at the hands of K'Kruhk's lightsaber. After witnessing K'Kruhk's rage, the youngling began to show signs of succumbing to the dark side, until finally on the planet Arkinnea, she gave into her rage to crush a group of Arkinnea Militia that were pursuing them to eliminate them as witnesses to the militia's murder of refugees after believing that the militia had killed K'Kruhk. Despite the Jedi escaping to the Hidden Temple on the world, Sidirri would eventually flee the temple. Jedi Master Zao would set off in pursuit of her, but neither would be seen again by the Jedi in the temple.
Since her creation, Sidirri was intended to be the woman who attempted to become Darth Vader's apprentice before being killed by the Dark Lord himself on Dargulli.