Senni Tonnika was a female who, in conjunction with her sibling Brea, made up the Tonnika sisters, a pair of swindlers. Sometime in the past, Senni and Brea aided a colleague in escaping from jail.
Senni and Brea eventually encountered Lando Calrissian and wrecked their apartment on Coruscant to get a ride on the Millennium Falcon. They also met Han Solo, but he later double-crossed and embarrassed the sisters, which resulted in the end of their partnership.
Around 0 BBY, not long before the Battle of Yavin, Tonnika and her sister resided on Tatooine, but when Jabba placed a reward on Solo's head, they went to Chalmun's Spaceport Cantina, a bar situated in Mos Eisley. She and her sister observed recluse Obi-Wan Kenobi defending his student called Luke Skywalker and fend off two wanted criminals, injuring Physician Cornelius Evazan and severing Ponda Baba's right appendage before they decided to forgo collecting Jabba's reward, and instead steal the Millennium Falcon to leave the planet, after overhearing the ship was in Docking Bay 94. Upon arriving at the bay, they quickly needed to conceal themselves due to Jabba's presence. They slipped out of the docking bay, and resolved to steal a different ship.
Senni's character was portrayed by Angela Staines, while Brea's character was played by the actress Christine Hewett. Christine and Angela were friends in real life and were referred to as "Space Girls" during the production.