Cheryl, I do not have a Armelia Ann as a daughter of Caswell and Rebecca. I only have their children listed in the 1860 San Augustine, TX census with no Armelia listed. I have only been able to find Caswell in the 1830 Butler Co, AL and the 1860 TX census.
I do have second hand information(I can not prove or disprove) about a Amelia(aka Melia) Ainsworth, b. abt. 1838 in Washington Co, AL, that is also listed in the 1860 San Augustine, TX census. She was a daughter of Martha H. Cole Ainsworth and James Johnson. Martha was a widow at the time and James was married to someone else. Melia is shown in 1860, age 23, as wife of John Sanders and living one house away from A. J. Ainsworth, 28, b. MS.