She's definitely a natural beauty, but I feel like they deliberately muted her looks for this role. The short haircut is cute in a pixie way, but it's not the flowing luscious hair that Godard's other starlets would flaunt in sexy roles (Bardot, etc). I think Godard often cast gorgeous women in mousy roles, downplaying their sexuality in favor of their cuteness/innocence (Anna Karina in Band of Outsiders...again with the flat pixie hairdo).

But yeah it was kinda weird in this case that the dialogue made a point to talk about how 'unattractive' she is, when that was clearly not the case. Unless the point was to show that Michel was deliberately withholding compliments? That's a possibility too. His character is the type of guy who never gives anyone a compliment because he's too wrapped up in himself to admit anyone impresses him. Michel does slip up and betray his ambivalence at the end when he tells her she could easily be a model at the photography studio.