Susan Bravely was once a Podrace champion throughout the Galaxy. But one day a race was attacked by Imperial Forces for it was deemed illegal by the Emperor.
Susan managed to evade the Imperial Troopers in her podracer and fled the system before getting caught.
She found shelter at Yavin 4, where she was later found by The Fire Skeleton and the other Rebels. She was told everything about the Emperor and the Empire and decided to join the Rebelious movement and lend her race and vechile abilities for them to use.