It's important to note that the attire in this picture is very purposefully French. As was the custom for foreign princesses about to marry French dauphins, young Marie Antoinette was welcomed into her new country with a ritual where selected court members removed all of her native clothing, including any jewelry or other accessories, and outfitted her in the wedding finery of France.
The dress that Marie Antoinette wore for her actual wedding day was yet another gown. The pearl-encrusted white dress, which featured elaborate hoops, underskirting, and inlaid jewels, was also quintessentially French. It was a visual affirmation of Marie Antoinette’s dedication to her new country.