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Franco was born on the west coast of France and began her career playing for Avenir Maritime Laleu in her hometown. She later moved to ES Rochellaise before securing a move to D1 Féminine club ASJ Soyaux at the start of the millennium. Franco spent two years in the youth system before making her league debut during the 2002–03 season. In her debut season, she scored four goals. The 2003–04 season saw Franco's opportunities in the team increase as she was given a permanent role in the starting eleven. Over the next four seasons, she appeared in all 22 matches scoring double-digit goals on two occasions. In her final season with Soyaux, she appeared in 19 matches scoring seven goals. Her successful seven-year career gained the attention of defending champions Olympique Lyonnais and Franco eventually secured a move to the club.
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