Zerby joined the group, then called Teens for Christ in 1969. After becoming a private secretary to David Berg, the group's founder, a sexual relationship started between the two. In a prophecy titled "A Prophecy of God on the Old Church and the New Church", Berg explained that he had been told by God to leave his first wife, Jane Miller, who represented the "old church", for Zerby who became his soi-disant second wife, who represented the "new church".
In 1988, with David Berg's health declining, Maria began to take a leadership role within the group. Upon his death in October 1994 she assumed full leadership of the group and married her long-time partner, Steven Douglas Kelly (known in the group as Christopher Smith, Peter Amsterdam or King Peter).
- King County Name Change Order - Documents Karen Elva Zerby name change to Katherine Rianna Smith (11/04/1997)
- House, H. Wayne (2000). Charts of Cults, Sects, and Religious Movements. Zondervan Publishing Company. ISBN 0310385512.
- Lewis, James R. (2004). Controversial New Religions Oxford University Press. ISBN 0195156838.