Sidotti Cho was a freelance peacekeeping agent — crudely referred to as a bounty hunter — active within the jurisdiction of the Shadow Proclamation. Her long-standing business partner and best friend was Meklit Bokassa.
Even from a young age Sidotti was possessed of a useful degree of common sense. Though not enough to prevent her deliberately indulging in risky behaviour — including her penchant for 'gut' decisions that far more often than not paid off — she always knew to take steps to minimise the effects of (catastrophic) failure. This would most often present itself through meticulous planning of and for important situations, and would often complain when situations ran counter to her expectations. She was, in short, not the most trusting of people.
She underwent a noticeable behavioural shift during her encounter with the Doctor as a result of interacting with the telepathic fields of both the TARDIS and the tesseract vessel Ardheredh, demonstrating a more mellow outlook typical of her partner.