Together with her family and others, Heikel played a central role in the beginnings of the Baptist movement in Finland. At the time, all religious gatherings outside of those of the
Evangelical Lutheran Church of Finland were forbidden by the
Conventicle Act, "used to restrict the pietistic revival movements in Finland". In 1859, a number of members of the growing Baptist movement in
Åland faced hearings in front of the Bishop's Chapter at the
Turku Cathedral. Among the Lutheran clergy present was Henrik Heikel, who took an interest in the Baptists' beliefs and spoke to them to learn more, although he did not convert. After moving to Pedersöre in 1860, the Heikel family maintained a connection with the Baptists in Åland. After Henrik Heikel's death in 1867, both Anna and her brother Viktor were baptized in Stockholm by
Anders Wiberg; Netta was also baptized. After her return, she began to hold meetings and share material on Baptist teachings. Heikel and her circles were influenced by the teachings of
Carl Olof Rosenius and the
Nyevangelism () movement. The family received a visit from a Baptist pastor who had been at the hearing with Henrik Heikel ten years earlier; together they held meetings and the pastor's preaching led to more conversions. Four members of the Heikel family, along with nine others, founded a Swedish-language Baptist church in Jakobstad in 1870. At one point she was called to a hearing at the
cathedral chapter regarding her conversion; there she was defended by Alopaeus, who, while not Baptist himself, supported her beliefs. Her beliefs were also controversial in the community and forced her to leave teaching for a time. Anna and Netta would eventually leave the Baptists and join the . == Sunday school ==