#1 Alicia Sheridan LeFanu (1753-1817), Irish playwright, author of The Sons of Erin, married Joseph Lefanu in 1981. She was the older sister of Elizabeth "Betsy" Sheridan who married Capt. Henry Lefanu, and the aunt of Alicia Lefanu.
#2 Alicia Lefanu (1791-after 1844), Irish poet and daughter of Elizabeth "Betsy" Sheridan Lefanu. She was the niece and namesake of #1. She wrote poems and novels, including Strathallan and Leolin Abbey.
It's her mother Betsy (1758-1837) who was the author of Helen Monteagle and Lucy Osmond.