Shirna was a Lurman showman.
Shirna travelled with Vorg to Inter Minor by cargo thruster to demonstrate the scope as part of a show. When they were received with suspicion, she wished she had never come, saying she should have stayed with the All-Star Dance Company, her former employers.
Despite these difficulties, she helped the Third Doctor get back in and out of the scope to rescue Jo. (TV: Carnival of Monsters)