Looking for Martha Byrum

I found Leavy's mother's name in various documents, to be Mary Louise Byrum. That surname is also bothersome. It could be Byram, Byrum, Bynum, or even "Barren" in various interpretations. 

The death certificates of her children who lived long enough verify that.  Thomas Mellon Starnes 1936 death certificate lists his mother's name as "Mary Byrums". The one for Frederick Layfayette "Fate" Starnes declares his mother as "Mary Brooms", informant, his son Silas Grier Starnes.  Della Starnes McAnulty's death certificate names her mother as "Mary Barren".  I have not been able to locate the death certificate for oldest daughter, Sarah Alice Starnes Linker, in either Cabarrus or Mecklenburg counties, but her obituary claims she passed away in Mecklenburg County while visiting her daughter and was buried at Rocky River Presbyterian Church in Cabarrus County, where she was a member.

Also buried at Rocky River Presbyterian Church with Mary Louis Byram Starnes are her children who died young:

Martha Ann Starnes, age 11, September 9 1865 to March 18, 1877.
Georgia Ann Starnes, age 7, January 9, 1873 to August 4, 1880.

Oldest son and first child to pass away was John H. Starnes, age 9, born May 1, 1858 in Union County and died December 9, 1867 in Cabarrus County and is buried in a small cemetery, which was probably a neighbors family.

The other child who lived long enough to obtain a death certificate (which began around 1912, a little earlier or later in some counties), was my very own Great, Great-Grandmother Leavy. I located her tombstone and although she passed away in 1939, I have not located her death certificate. She may have been hospitalized in another county.

This makes Mary Louise Byrum my 3rd Great-Grandmother. 

The 1880 census takes me back one more generation. In it, a 70 year old Martha Byrum is listed as the Mother-in-Law of F. F. Starnes, my 3rd Great-Grandfather, meaning she was the mother of Mary Louise Byrum Starnes. 

This makes Martha (maiden name yet unknown) Byrum or Byram my 4th Great-Grandmother. But who was she?

This census tells us she was born in South Carolina about 1810, that she is a widow in 1880, and that both of her parents were born in South Carolina. Her daughter, Mary L., on the other hand, was born in North Carolina about 1837, her mother being born in South Carolina, and her father in North Carolina. 

And at this point, this is about all of the information I have on the mysterious Martha Byrum.

Being alive in 1880, it seems I should be able to find her in the 1850, 1860, and 1870 census records. She may have been missed in one, or even two, but all? This puts Martha as my lady of mystery. What was her maiden name? Who and when did she marry? Where was she from 1850 until 1880, this South Carolina born lady. It seems likely that she may have been from either Lancaster or York Counties, and may have lived in Union County at some point.

A girl fitting the correct initials for Mary L Byrum, who married F. F. Starnes, shows up in the 1850 census of Union County, NC, not very far from where Fred Starnes Sr. (actually about the 4th or 5th in a long line of Frederick Starnes), Frederick Fincher Starnes father, is living. She is the right age, 14. I am almost sure this is my Mary Louise, but then, who are the other folks in the household? If I can find out more about them, perhaps I can solve one more mystery in the family tree.