The will of Edmund McAlister states "I give and bequeath unto my appointed daughter Luisa Blankenship child of Margaret Blankenship all my estate real and personal on condition that she take name of McAlister". Her name was changed in 1835 by an act of the Alabama legislature. She was sent to the Utica Female Academy in New York for education.
Based on the census data she appears to have been born in Alabama about 1824 not 1812 as many sources mention. Her oldest child was 7 in the 1850 census and he was born in Alabama. So, she likely married WIlliam there. No marriage record found.
Based on the census data, she had at least 8 children
Joseph Warren b 4/15/1842 Alabama - his biography is at d 7/13/1904
Mary E b 1/15/1847 Mississippi, married William L Hemingway. She died 12/3/1935
Ann Elizabeth b 1848 Mississippi - last found in the 1870 census age 20 and single living at home with home.
Jeannie b 1855 Mississippi - who may have died between 1860 and 1870
Sallie b 1857 Mississippi, married Allison Topp and she died 3/31/1887 
Henry Pinkney b 1/23/1861 Mississippi d 7/24/1941 and is buried at Arlington Cemetery
William H born 1863 Mississippi - last found in 1870 census
The 1850 census shows her age as 26 - she is in the household of Thomas Peete with her husband and 3 children. Their relationship with the Peete family is unknown. Perhaps the census taker just numbered the household incorrectly.
The 1860 census shows her age as 36 - she is listed as L McCain with WA McCain and 7 children are in the household with ages from less than a year to age 17. All children were born in Mississippi except the oldest JW who was born in Alabama.
The 1870 census shows her age as 45 - she is listed as M Lor Mccain with 4 children ages 7 to 20 in the household.
The 1880 census shows her age as 56 - she is living with her son John and his family and her two unmarried children Sallie and Willie.
Although no tombstone is shown, findagraveshows her birth as 12/2/1812. She is buried in
Waverly Plantation Teoc, Carroll County, Mississippi, USA
↑ Perrin etal, Kentucky, a History of the State, Southern Historical Press, 1887. Page 818.
"United States Census, 1850," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:M4LN-8J9 : 12 April 2016), Louisa Mc Cain in household of Thomas Peete, Tallahatchie county, Tallahatchie, Mississippi, United States; citing family 361, NARA microfilm publication M432 (Washington, D.C.: National Archives and Records Administration, n.d.).
"United States Census, 1870," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:MFS8-2T7 : 12 April 2016), M Lor Mccain, Mississippi, United States; citing p. 4, family 27, NARA microfilm publication M593 (Washington D.C.: National Archives and Records Administration, n.d.); FHL microfilm 552,222.
"United States Census, 1880," database with images, FamilySearch (https://familysearch.org/ark:/61903/1:1:M4G9-V1M : 12 August 2017), Mary L Mccain in household of John Mccain, Beat 2, Carroll, Mississippi, United States; citing enumeration district ED 19, sheet 31A, NARA microfilm publication T9 (Washington D.C.: National Archives and Records Administration, n.d.), roll 0642; FHL microfilm 1,254,642.
Will of Edmund McAlister, Lawrence County, Alabama. Probated 1838.
Alabama Laws and Joint Resolutions of the Legislature of Alabama, 1835. Act No. 71, page 80.