American movies ALWAYS screw-up royal forms of address
In the scene where the Duchess of Polignac (played by Rose Byrne) first meets Marie-Antoinette during an opera performance, she refers to the Dauphine as "Your Majesty", when in fact she would have been referred to as "Your Royal Highness". "Majesty" is only reserved for a Monarch and/or a Queen consort. Considering the iron clad etiquette and insane royal rituals that existed at the French court at that time, the Duchess would NEVER have made such a gaffe in the presence of the heirs to the throne!