Zerby was raised in evangelical Pentecostalism. Her father was a Nazarene minister, and she is credited with bringing the "fundamental Pentecostal principle of being 'Spirit-led'" into the movement she eventually came to lead. She joined the group, then called Teens for Christ, in 1969. Trained as a stenographer, she became the personal secretary to David Berg, the group's founder, and instrumental in transcribing his classes. He later separated from his first wife, Jane, and Zerby became his wife. Berg openly explained this to his followers via a missive called "The Old Church and the New Church". In 1975, while living in Tenerife, Spain, Zerby had a son, Ricky Rodriguez, who was to "guide them all when the End Times came". Rodriguez's childhood was recorded in a book called The Story of Davidito, which was meant to be an example to other members on how to raise their children. The book is controversial for its alleged encouragement of child sexual abuse. According to the book, Zerby participated in the alleged sexual abuse of her son, alongside David Berg, from the time he was 18 months old, and allowed her seven-year-old daughter Christina to be raised in a similar manner. The church leadership in this period was highly secretive, living in remote locations and being barely seen by anyone; Zerby was known to the church's followers mostly from cartoons in the Berg-penned MO Letters. In January 2005, Rodriguez murdered former group member Angela Smith, a former nanny; hours later Rodriguez committed suicide. In a video recorded the night before, "he said he saw himself as a vigilante avenging children like him and his sisters who had been subject to rapes and beatings". Apparently, he had been looking for his mother and for his stepsister: "He wanted to see his mother prosecuted for child abuse, and to free Techi from the group". By the mid-1980s Zerby had become important enough to issue church edicts of her own: in 1984 she forbade sexual activity for new members until they had been in the group for six months, and in that same year began the taping of cassettes with music, which provided an additional source of income. In 1986 she forbade sexual contact between adults and minors; later it became an offense that could lead to excommunication. Throughout the 1980s she dictated and enforced elements of discipline, ending for instance a training program for children she deemed too harsh. With David Berg's health declining in the late 1980s, Zerby, having been groomed for the position, essentially took over the leadership position in 1988. After Berg's death in 1994, she married Peter Amsterdam, another church leader, and assumed the spiritual leadership of the group.
