She had eight older siblings: Alvin, Hyrum, Sophronia, Joseph Jr., Samuel, William, Katharine, and Don Carlos.

[1]: 7  As Lucy Smith grew up, she helped take care of the family farm by "hauling wood, gathering sheep, milking cows, and preparing meals.

"[2]: 401  When she was ten years old, her sister Sophronia had a baby, Maria, and Smith helped care for her new niece.

While he was gone, a mob came in search of Hyrum Smith and began to ransack the house until Lucy's brother William forced the men to leave.

[1]: 9 In May 1831, nine-year-old Lucy Smith moved with her family to Kirtland, Ohio to join the growing body of Latter Day Saints there.

[5] In 1838, as tensions mounted among the Latter Day Saints in Kirtland, the Smith family moved to Far West, Missouri.

[3] Smith was also one of the first people in the church to participate in baptisms for the dead,[2]: 410  serving as proxy for her aunt Lovina Mack,[9]: 280  who had died in 1794.

During this time, Millikin joined a committee whose task was to encourage "apostates" (those who had left the church) to leave Nauvoo.

In September 1846, the Millikin family fled Nauvoo due to conflict that had arisen, and settled in Knoxville, Illinois.

[9]: 108 When the succession crisis in the Latter Day Saint movement occurred, Millikin chose not to follow Brigham Young's group west to Utah Territory; instead, she settled in Fountain Green, Illinois to live near her sisters.

[12]: 167–70  Lucy Millikin was "received" into the Reorganized Church of Jesus Christ of Latter day Saints on April 8, 1873,[5] but was involved in the faith only minimally.

[2]: 422–23 Lucy and Arthur Millikin moved to Colchester, Illinois, forty miles from Nauvoo,[3] in 1856[4] to avoid persecution and find economic opportunity.

[3] Lucy Millikin died on December 9, 1882, in Colchester[13] after contracting a respiratory disease while caring for a sick daughter-in-law.