From a history found on familysearch.org:

Fannie is a daughter of John Van Cott and Lucy Lavinia Sackett. Her father was a prominent, well-to-do leader in the community and Church. Fannie grew up in Salt Lake City. In 1868 and 1869 Fannie was working as a telegraph operator in Provo, Utah. She met Alexander F. Macdonald. They married in the Endowment House on Temple Square in Salt Lake City on August 1, 1870.

Alexander and Fannie became parents to five children born in two states and two countries: John Van Cott (1872-1883), Scott Van Cott (1875-1876), Byron Van Cott (1877-1953), Lucy Lavinia (1884-1949), and Flora Hermosa (1888-1921).

In 1872 Alexander was asked by Church leadership to move to St. George. They were there while the St. George Temple was built. For three years Fannie and sister wife, Elizabeth, got up at 3:00 a.m. to pack lunches for 70 men and then prepared breakfast for 80 men in time for them to report for work by 7 a.m.

After the St. George Temple was dedicated, Alexander was called on a mission to Scotland. His wives were left to fend for themselves and their children. Fannie and Elizabeth again worked together. In December 1879 Alexander was called to Mesa, Arizona. Fannie settled into a home where she operated a store and post office. In 1883 a smallpox epidemic swept through Mesa. Fanny lost her eleven year-old son, John.

In the 1880s the U.S. Federal Government became more and more aggressive against the Mormons because of their practice of polygamy. Alexander was finally forced to take his wives and families into Mexico. Alexander built Fannie a concrete home in Colonia Juarez. Here she operated a post office, had a good vegetable garden and fruit trees, and raised her children. Alexander died in 1903. The Mormons were forced out of Mexico by the revolution in 1912. Fannie's son, Byron, stayed in the Colonies and as soon as it was safe, Fannie returned.

Byron married in 1904. Lucy married in 1909. Flora married in 1912 and then tragically died in 1921 leaving four children. Fannie moved in with her son-in-law to care for his children, living there about nine years until he remarried. Then Fannie moved to Lucy's comfortable home, living her last years there. She was buried in the Colonia Dublan Cemetery.