This woman started out as a daughter of John A, known from his 1870 Census listing. Then in 1880, Amanda 27, Emma 25 and George B 18 (Mertz all three) live in the Scott Lebard household with his wife Lenesa (it looked like) age 24 in Lewisburg. The Mertzes are listed as sister-in-law or brother-in-law to Scott. So everything fits that Lenesa is Louisa, the parents have died (confirmed by their tombstones), and her brothers and sisters live with her and her husband. The final puzzle piece is her tombstone in Lewisburg which says Louisa Gertrude wife of W S Lebard found in the Mertz plot.