Her death date and place - Het Boek van Gestorwene (Book of deaths), Land van Waveren - https://www.familysearch.org/ark:/61903/3:1:3Q9M-CSKD-F3LY?cat=993684 (top of page)
Hi Sharon
In my opinion it is a mistake to remove the 'Willemsz' as it does not refer to her husband Willem.
The 'sz' was a Dutch extension to denote who the father was. In other words it translates as Martha (Daughterf Willem) van der Merwe. In this instance it refers to Willem van der Merwe the Stamouer ( see https://www.stamouers.com/stamouers/surnames-v-z/523-van-der-merwe-... ). When referring to the Orphan Chamber and VOC records, we often more easily trace the lineage in the Cape via those 'sz'. Linguistically it is correctly recorded.
"Machtelt van der Merwe wedw Pieter Willemsz Heerde" died Feb 1765, Tulbagh
https://www.familysearch.org/ark:/61903/3:1:3Q9M-CSKD-F3LY?cat=993684
d.o. Willem Schalk van der Merwe and Elsje Jacobs Cloete
Martha "Marritje" van der Merwe x Willem Pieter van Heerden
I reckon:-
"Maartje van der Merwe wedw Willem van der Merwe" died 2 Mar 1784, Tulbagh"
https://www.familysearch.org/ark:/61903/3:1:3Q9M-CSKD-F3DS?i=434&am...
d.o. Schalk Willemsz van der Merwe and Anne Prevot/Prevost
Which Magteld van der Merwe died 5 Dec 1759, Tulbagh - https://www.familysearch.org/ark:/61903/3:1:3Q9M-CSKD-F3GQ?i=425&am...
so
Martha van der Merwe bap 14 May 1713 - 2 Mar 1784, Tulbagh
do Schalk van der Merwe & Anne Prévost
x 30 April 1730 Willem van Heerden (so Pieter Willemse van H & Magteld van der Merwe)
Magteld Willemsz van der Merwe (c 1691- Feb 1765, Waveren)
do Willem Schalks van der Merwe & Elsje Jacobs Cloeten
x 1708 Stellenbosch, Pieter Willems van Heerden (c1682-1763)
I find it curious that Geni takes a different approach to Wikitree. For example the note on this profile explains as follows:
" ↑ Martha will be profile protected with the LNAB being Willemse though this isn't strictly correct given the time frame - patronymically she would have been noted as Schalks[e][dr], not as Willemse (van der Merwe not even being mentioned), however at this time the naming system was already in transition to the more modern system and following WikITree policy we have to note exactly the LNAB as can be read on the baptism".
While I understand the need for documented proof, keeping to the LNAB seems to be a strategy with merit for thos very old records.