I am an occasional Smock researcher (they are kin through my Teeple cousins).
As you mention, the 1900 census from Lincoln Co., KY has Julia as the daughter of Samuel and Sallie Smock.She is 11/12s year old b. Jun. 1899.Her SSDI record says 25 June 1900.I think it is the same Julia.
Samuel died of pneumonia 3 Jun 1913 in Lincoln Co., KY.Death certificate says he is widower and his father is Isaac.Ancestry has the 1910 Census but Julia is indexed as Jufia.Her brother Charlie did in December 1913 and his parents were Samuel and Sallie Belle (Turner) Smock.1880 Census for Marion Co., KY has Samuel 22 married to Sallie 18.
Samuel was born to Isaac (mother's name not given) on 26 November 1856. (Source: Death Certificate)
1860 Census for Isaac and Catherine Smock in Casey Co., KY indicates Isaac was born about 1814 in Mercer Co., KY.
Various Smock researchers link this Isaac Smock to Abraham Smock who married Mary Stagg.Abraham/Abram Smock connects back to the colonial Dutch family.
Samuel Lee Smock (1856-1913) does appear to be the father and Saliie Belle Turner (b. Kentucky, not Holland) is her mother.Lots of mysterious dates and probable confusion about similar names nay have lead to other years you have seen.Her name in 1910 is given as Margaret and/or Mary.She would of had to die between 1910 and 1913 if the death certificate is correct about being a widower.