1870 Census. DeKalb Co, TN, Hh 106
1880 Census. DeKalb Co TN, Hh 184
Said to be buried Spring Hill Cemetery, Nashville, TN. FindAGrave has three Elizabeth Johnsons buried in that cemetery, but none can be this lady.
Elizabeth DENNIS and Isaac Carroll JOHNSON were married on 17 December 1865. They were divorced on 18 May 1906. Isaac Carroll JOHNSON was born in 1839. He died in 1913 at the age of 74 in Cannon County, Tennessee. He was buried in Gunter-Grizzle Cemetery, Half Acre, Cannon County, Tennessee.
1850 Census. Dist 5, DeKalb, TN
A Carroll Johnson, age 11, was with a William & Nancy Johnson in the 1860 Census, Dist 9, DeKalb, TN. I don't think he can be the same.