S.A BDM records are not on line- you could try some of the larger libraries that have genealogical data or join a Genealogical Society.
Found the following marriage record:
Groom: LOUD Given names: Edward Bride: MATTERS Given names: Sarah Date: 1862-05-01 Groom Age: 22 Status: S Groom's Father: Edward LOUD Bride Age: 18 Status: S Bride's Father: William MATTERS Place: St Stephen Church Willunga District: Wil Symbol: Book/Page: 50/55 Cross Reference:
Birth of a brother
Surname: WATTERS Given Names: William Date: 1857-05-10 Sex: M Father: William WATTERS Mother: Mary HOLMAN Birth Place/Residence: Willunga District Code: Wil Symbol: A Book: 12 Page: 27 Cross Reference:
As you can see HOLMAN is the mother's maiden name and the family name was more likely to be WATTERS rather than MATTERS
This is most likely her birth:
Surname: WATERS Given Names: Sally Date: 1856-01-28 Sex: F Father: William WATERS Mother: Mary HOLMAN Birth Place/Residence: Willunga District Code: Wil Symbol: M Book: 5 Page: 347 Cross Reference:
Again the WATERS is most likely an error in the register and the surname most likely again to to WATTERS, she may well have adopted the name Sarah as opposed to her birth name of Sally.
I hope this is of some help Good luck Regards Gordon