In 0 BBY, Isabella was seated at Chalmun's Spaceport Cantina when she was approached by two farmboys, stepbrothers Phineas Flynn and Ferb Fletcher, who had recently recovered the a disk containing the plans to an Imperial battlestation, the Death Star. Flynn explained to Isabella that they needed a pilot to pursue a ship that had just left Docking Bay 94, which Isabella recognized as the Millennium Falcon. Isabella explained her rivalry with Solo to the boys. Upon hearing the Twi'lek singer Vanessa performed a song containing the lyric "so low," Isabella fired a blast in the direction of the stage, deciding to accept the job and leave.
Isabella and company pursued the Millennium Falcon aboard the Centennial Chihuahua. To avoid being detected by the Empire, Flynn and Fletcher modified the Chihuahuas deflector shield to act as a cloaking device. Flynn later entrusted Isabella with the Death Star plans to ensure their safe delivery while he remained behind to rescue Fletcher.
Isabella delivered the plans to Rebel technicians on Yavin 4. Despite an initial reluctance to further involve herself with the Rebellion, an encounter with Han Solo and Chewbacca caused Isabella to reconsider. Isabella then returned to the Death Star to rescue Flynn and Fletcher.
Isabella attended the Royal Award Ceremony afterparty on Yavin 4. During the celebration, she kissed Flynn.
Although she maintained a gruff attitude at times, Isabella came to form an attachment to Phineas Flynn and Ferb Fletcher. She also maintained a rivalry with Han Solo, such that the mere mention of his name could irritate her.