One reason T. Kerwin asks for more information is that there is no Geneva E. Martin born 1924 in South Carolina listed in the 1940 census. Are you sure of the year 1924?
Did she live in South Carolina in 1930 and 1940, do you know? Do you know the town and/or county where Geneva was born, or grew up?
That 1940 census is free and searchable at Ancestry.com, so you can check that out yourself if you wish. (Other census years require you to subscribe to Ancestry.com - or to access it at your local library). Similar people do appear in the 1940 census, however.
Do you know her sisters' names? Dates Of Birth? Again, the more information the forum has, the more possible it may be to identify her among the "candidates."
Is it possible Geneva was married in 1940 (and thus listed with husband under her married name)?
Another resource for you is Find a Grave. If you know her married name, and date and place of death, you can search for her there. It's possible (a long shot) that a memorial for her there could include her parents' names.
I did not find Geneva E. Martin on Find a Grave but many times memorials on that free website do NOT include a woman's maiden name.
Also with death info, a volunteer may be able to locate an obituary, which might include her parents' names. Volunteers in a person's county of death sometimes look up obits for seekers. Some volunteers on Genforum have subscriptions to online databases of obituaries.
Obituaries for Geneva's siblings also might reveal the parents' names. By adding information about them (spouses, places they lived, when/where born and died, if deceased) could lead to information about Geneva's birth family.
Online genealogy forums avoid listing information on living people because of privacy concerns, so use your judgment and person knowledge on that one.
Sorry we didn't find her right off the bat - but as you can see there are certainly avenues still to be explored.