What does Wu Chun-Mei want Adeline to do that she has never done before? Why couldn't Adeline do this? in chapter 13 of Chinese Cinderella

She wants Adeline to lie about going to her party. Being one of her closest friends at school, Chun-mei invites Adeline over to celebrate her birthday. Adeline insists that this is impossible, trying to find excuses due to her knowledge that Niang would never allow her to attend a party. However, an opportunity arises in a day off from school, special to her academy only. Since her parents don’t know about her school schedule, Adeline pretends to go to school but instead attends the party.