User blog comment:J Fan/Pirates 5 - Sequel News Rundown/@comment-1984959-20130722181441/@comment-1984959-20130728010741

Uskok was just speculating. Just to clarify: Giselle never had a sister in the franchise (not that we know of at least), and even if the character existed she hasn't appeared in the film - only Giselle herself. ;)