"David Miscavige has now become the 'leader' of the Scientology religion. Yet what LRH left behind was a huge structure to properly manage all aspects of the Scientology religion. He put a complete and brilliant organizational structure there, not one individual. There never was supposed to be a 'leader' other than LRH himself as the goal maker for our group," she wrote.
The church disputed Cook's claim, comparing it to a criticism of the Catholic pope's having too much power over the Catholic Church.
"Apostates are known to be unreliable with respect to their former faiths," the lawyers wrote in a letter. "[Cook is] not qualified to speak about church finances, as she never worked for the Church of Scientology International, the mother church that controls finances."
Rathbun, who left the church in 2004 and who the church has called a "liar" and a "heretic," said that Cook was formerly high-ranking enough that her email would be taken seriously by followers.
"She was one of the most prominent members in the entire world," he said. "Virtually any Scientologist who's been involved for very long has actually had face time with her, as a very respected person."
During her years of employment with the church, Cook worked at Scientology's Flag service org in Clearwater, Fla., according to a letter from the church's attorney. Rathbun told ABC News that Cook was the captain of Flag, a position he described as "president or CEO." Many church members who are progressing in Scientology are expected to visit Flag for courses and training, Rathbun said.