You need to look at the 1820 Census, Williamson County, TN, page 50.
Cloey Randolph is listed as the head of the household which would mean that her husband John was deceased.
She has the following in her household: One male 10-16 One Female 10-16 One female 16-26 One female 45
The family below her is Thomas McCrackin and then Lancaster Ragsdale.
Lancaster Ragsdale has the following in his household: One male 1-10 One male 26-40 One female 16-26
In the 1830 Census John C. Randolph is in Hickman Co., TN. I do not find him in 1840.
Are you sure that the John Randolph will in Lauderdale County, AL is not the John C. Randolph who married Dicey Ragsdale in Williamson Co., TN on 8 June 1819?
That would be the reason Mary Heron Randolph was not mentioned in the will, she was not a daughter, John B. Ragsdale was mentioned because he was the guardian of Catherine the daughter of John C. and Dicey.
Maybe we should look for a will for John Randolph husband of Cloey back in VA or NC sometime before 1820. The Ragsdale's came to TN from Moore County, NC.