They haven't confirmed the origin of Fleurdelys's appearance right? For some reason I assumed she grew to that size in the tower but looking back now, she had the appearance of Carty before and after the fight, so maybe it was like a manifestation of Imperator/Leviathan's power in an ideal vessel. The resonator showcase uses Fleur's model but I don't think she looked like that in the past, it's framed like a nightmare Carty had before entering Septimont.