The Mary E. Houston that you are looking at died in 1865 and is buried in Dyer Cem - as is her daughter Gab. Bennett. (See findagrave.)
It appears that Hester and Susannah moved to Louisville, Jefferson, KY after their mother's death.
1870 Louisville, Jefferson, KY Deland, Mike 36 IRE House Painter Martha 25 ALA Mary 3 KY Casteel, Martin 37 IRE Laborer Kate 35 IRE Wash woman Mary 16 KY Shoe Binding Mat 14 KY (male) Julia 5 KY Houston, Hester 37 MS Wash woman Houston, Susana 35 MS Wash woman
Looks like Hester may have married or more likely died.By 1880 Susannah is living at the Jefferson County Poor House.
Looks like she lived there off and on for the rest of her life.Never married.
KY death Cert - Susie Houston b. 10/1/1833 MS d. 10/22/1913 Jefferson, KY father - William Houston mother - Mary Sullivan Informant - J. K. Westfall (He ran the almshouse)
I found the tree you got your info on Hugh & N L Houston from. They have taken bits and pieces of several totally different families and put them all together.You should disregard it, as it is worthless.