Thanks to Steel!

Sister of Starfire, Blackfire came to earth after being hunted down by the Centari Police, Kai and Cron, for commiting "high crimes" throughout the entire Centari system. Attempting to frame her sister as the culprit, she gives Starfire a Centari Moon Diamond necklace--making the police think it's Starfire even more.

Blackfire is eventually found out, however, as Starfire and her battle. In the end, Blackfire slips up and is taken into police custody. Before being taken away, Blackfire called out to Starfire, telling her that "I will get out of jail, little sister, and I will get even."