After going to primary school in her birthplace, she studied at the Potchefstroom University for Christian Higher Education and in 1941 obtained her Bachelor of Arts in social sciences.
Due to the massive size of the congregation in area and the paucity of GKSA pastors in SWA, her husband was often home only a few days a month.
In 1951, they started the Gereformeerde Sustersbond ("GKSA Sisterhood") and socially contributed to founding 17 chapters of the Vrouelandbou-unie (VLU, "Farm Women's Union") throughout SWA.
She was chairwoman of the Sisterhood and the executive committee of the VLU, commander of the Suid- Afrikaanse Noodhulpliga ("South African First Aid League") in SWA, and a PTA member.
Braam le Roux, recalled Annie van der Merwe in 2017 as "an impressive, independent, and loving human being.