What holiday does Hazel’s mother declare in Chapter 3? How does Hazel decide to celebrate?

Against her mother's normal procedure, her mom wakes Hazel up when it's almost 10 a.m. Her mother announces that it is Hazel's thirty-third half birthday, so they need to celebrate, in addition to Hazel having class. Hazel decides to celebrate with a trip to the mall with one of her girlfriends.