Last night, Yoona was going to tell Eunha and Lucas about the incident involving Jaeun and the flour. However, due to her embarrassment, she didn't utter a word. Nobody would brag about being humiliated in front of their class.
Since the ten thousand dollar tip incident happened, the story also dulled in comparison to Yoona's eyes anyways. The money completely reversed her personality. There was no need to linger on the bad. Throughout the day, all she was thinking about was what to gift her mother and friends as a thank you present. They've gone through a lot for her.
Now, she regretted not telling her friends.
If anything would go wrong, it would be a larger surprise to them in comparison to if she told them earlier about the flour incident. At least they would've expected the bullying to be this brutal.