Why might Yen Mah decide to start her tragic story with a joyous moment?

In starting her story on a positive note, the sunsequent chapters and revelations about her step-mother's abuse come directly to the forefront. Adeline did, however, have positive, loving, support in her life.... she knew the difference, and Aunt Baba, Nai Nai, and Ye Ye fulfilled the role of positive influences in her life.