Martha, I'm confused as to what you are asking? Do you think Martha Marie Smith was the daughter of Nancy Carver and Isaac Smith? Or the daughter of Nancy before they were married? Who are you saying was married in 1868?
Here is this family on the 1850 Columbia Co census and there is no Martha shown:
1850 Columbia Co FL Census- SMITH, Isaac, 53, farmer, $1000, SC SMITH, Nancy, 47, GA SMITH, Robert C., 25, farmer, GA SMITH, Caroline, 18, FL SMITH, William, 17, FL SMITH, Georgian, 14, FL SMITH, Bryant, 12, FL SMITH, John, 11, FL SMITH, David L., 7, FL SMITH, Elizabeth, 5, FL
There are a lot of researchers showing this family on Rootsweb WorldConnect and one does show Martha as only child of Isaac and Nancy Smith but does not show any sources to support it. Many researchers show this family and Martha is not shown as daughter.????