Sorry, but you apparently have been given some misinformation. Levi "BOONE" Helm did NOT have a sister named Lucinda Helm.
Levi "BOONE" Helm (1827-1864)was the son of Joseph Helm II (1787-1876) and Nancy Wilcox (1795- ).
His sisters were Elizabeth (1823-1845), Catherine (1826-1871), Mary (1830- ) and Martha (1834-1922).
Levi "BOONE" Helm was MARRIED to LUCINDA Frances Browning, daughter of Charles Browning. Levi "BOONE" Helm and LUCINDA Frances Browning were the parents of one child, Lucy B. Helm (b.1852).
Can find no connection to the Willis family. Sorry.