the moment you met Fran and balthier in the castle you can tell she's a strong character with a very well defined personality. If you see all the interactions between her and balthier you can see that he respects her a lot. Yes her clothing choices are iffy but that doesn't mean she's a walking doll. Even about the ocuria Fran has her own opinion.
I honestly don't agree. She barely factors into the story and she almost never has anything meaningful to say, outside of the storyline directly involving the Viera which is basically "Fran's very own episode".
Like it's cool if she and Balthier get along, but it doesn't translate into an active role in the story or a compelling participant in dialogue scenes. She's usually just there, like Penelo.