Glendora was the daughter of Carolyn (Carrie) Miller and Vernon Hamilton. Instead of using the name Glendora, Vance Hamilton's second wife, Pearl M. Hamilton used the name Louise according to Dick Miller. Glendora's middle initial is "L" and this probably stands for Louise, and her nickname may have been "Sis."
Sources
Florence Keble Beck (from a letter written by her mother, Louise Miller Kelble) and input by George Brundage in April 2013.
"United States Census, 1920," index and images, FamilySearch (https://familysearch.org/pal:/MM9.1.1/MDP5-KPF : accessed 19 Nov 2014), Vance Hamilton, Middletown Ward 3, Butler, Ohio, United States; citing sheet 4B, family 76, NARA microfilm publication T625, National Archives and Records Administration, Washington D.C.; FHL microfilm 1821352.
"United States Census, 1930," index and images, FamilySearch (https://familysearch.org/pal:/MM9.1.1/X4SZ-JGL : accessed 19 Nov 2014), Vance G Hamilton, Lemon, Butler, Ohio, United States; citing enumeration district (ED) 0026, sheet 22B, family 431, NARA microfilm publication T626, National Archives and Records Administration, Washington D.C.; FHL microfilm 2341488.
Find a Grave, database and images (https://www.findagrave.com/memorial/130828359/glendora-l-miller: accessed 12 November 2023), memorial page for Glendora L. “Sis” Hamilton Miller (24 Sep 1913–3 Jul 1991), Find a Grave Memorial ID 130828359, citing Williamsburg Cemetery, Williamsburg, Clermont County, Ohio, USA; Maintained by Barbara South (contributor 48494274).