There is a Sarah Keen in the 1850 Monroe County, Tennessee Census and I am trying to find her parents. Sarah Keen was born in 1823.
Next door, there is an Eli Keen and his wife, Nancy. There is a Sarah Keen in that family but this Sarah Keen is not his daughter.
In the 1880 Dallas, Texas Census, a Joseph Keen, born 1816 in Tennessee, is living with Sarah and her husband.
These are the only hints I have.