Her Royal Highness The Duchess of Cambridge has just entered, the guest of honour. The camera cut to Zara and her fake smile told it all. Why is Kate getting all the limelight, whereas Zara, the daughter of a Princess of Great Britain, probably considers herself more royal than the mere daughter of an air stewardess. Also Zara is an actual sportswoman and former winner herself and probably thinks herself more suited to be the main guest. Is Zara as green with envy as Her Royal Highness' dress?
You don't have to be a mindreader, it was live on TV and was obvious to see. Zara's smile was fake and you could see indignation and The Duchess taking precedence over her.