I always think Meghan looks great in casual wear over formalwear, but if she did wear Dior as a proper representative perhaps they would tailor their clothes to fit her.
I assumed that she borrowed the ones before, despite royal protocol insisting you pay people for their goods, so couldn’t have them altered like PoW who does pay for things and thus doesn’t have to send them back.
I also assume that she courts Dior for, among other reasons, the Diana connection, if she is trying reinvent herself as Diana Mark 2 (wince).