Princess Esmeralda before anything had gone straight to her father in her average dress telling him what she had noticed of the bride that had been replaced. The king didn't take this lightly but he decided that he would see to it himself. He would ensure that the veil of the fake bride was unveiled but not in the ballroom which would cause an uninvited conflict.
The king knew of the relationship between the crown prince and his lovely princess. They were unseparated but for her to have a speculation such as this, it meant something had happened between them and at the same time, she was only telling the truth.