Pan had a complete and complex character arc that spanned over a century. She started out as a stereotypical bratty kid interested in normal kid stuff like boys, dating, and fashion. She knew she was ridiculously strong compared to regular people, and that combined with her youth made her unable to comprehend how dangerous the sort of "adventures" Goku went on were. She saw going into space as a fun vacation, and didn't realize that her life would constantly be in danger. The decision to launch the ship prematurely and leave Goten behind wasn't born of selfishness or malice, but understandable ignorance and the mark of an ambitious free spirit.

When the shit hit the fan and it became obvious even to Pan that they weren't just on a fun sightseeing journey, her options really boiled down to two: she could let it overwhelm her and completely break her spirit (as would have happened to almost any other person, let alone someone her age), or she could knuckle down, embrace her heritage and family name, and let those events shape her and strengthen her. She chose the latter, and transformed from regular bratty tween to selfless, spirited warrior closely resembling her grandfather during his early adventures. In the end, she was ready and willing to make the ultimate sacrifice to protect the Earth, exactly like her father and grandfather had done multiple times before.

This all culminated in the aged, wise warrior we see in A Hero's Legacy, with Pan becoming a female Muten Roshi of sorts and keeping the Son family's spirit and teachings alive through Goku Jr., and by proxy Vegeta Jr. That film's title not only refers to Goku's legacy, but Pan's part in shaping and upholding it.

Pan's character development and personal arc are among the best of the series and in fiction. Hopefully Super doesn't ruin it with its tasteless retcon of her appearance and flanderization of her character like it has with so many other beloved characters.