Because Su Xiaofei had left the ball with Lu Qingfeng long before the 'Fairy of the Night' was announced, she had no idea that she had won the title and wasn't able to receive her award in person. Not that she cared about it anyway. She would rather go home early and rest to prepare for her meeting with the Yun family the next day.
It would also annoy the hell out of Ye Mingyu if she knew that Su Xiaofei didn't care one bit about the title she was dying to win that night. The things that she wanted, Su Xiaofei would naturally not compete with her for that, but it didn't mean she would waste the chance to mess with Ye Mingyu.
The next day, Su Xiaofei woke up early, despite wanting to sleep more. She forced herself to get up, brush her teeth and get dressed before going downstairs to find her mother busy preparing the things they would bring today.
