She was on Haidon when the Lucian Alliance attacked the planet. She, Li and Wang were the last of Haidon's defenses. They attempted to make it to the stargate but where ambushed by Corrin and his men. He killed the others but let her live, to act as a messanger to inform the planet Xi'an that they were coming they must surrender or die.
Shortly afterward, Cheung went to Stargate Command and spoke to General O'Neill and Colonel Everett Young about her people's situation. In order to get their interest, she also informed them that Xi'an held the secret of the ninth chevron.
Sometime later on Xi'an, Cheung caught sight of two soldiers she didn't recognize. When she chased after them, General Szeto stopped her and told her their conscripts. She then sought out Colonel Young for advice on following superiors and asked if he would help her. The two spied on Szeto and found him with two Lucian Alliance men.
Young and Cheung ran towards the city so Young could warn the Jaffa of the setup. Cheung readied herself for battle, knowing some of her men must still be loyal. They split up.
When Young and his men made it to the palace, they were ambushed by Corrin. Just as they were forced to surrender, Cheung killed Corrin from behind with her sword through his chest. Cheung's fighters then overwhelmed the Lucian Alliance soldiers.
Sergeant Ronald Greer tried to cover their escape until Cheung and her few remaining fighters told the Tau'ri to escape without them, as they would instead fight for the freedom once again. (SGU: "Icarus 1")