I'm not an authority on South African tennis by any means, but I was a huge Linky Boshoff fan in the 1970s. Here's what I know about that era of South Africans:
Boshoff retired at the end of 1978 after capturing the singles, doubles and mixed doubles title at the South African Open, beating most of her major South Africans rivals along the way. What an exit! She is best remembered for her stirring run to the Wimbledon quarterfinals in 1974 as a 17-year-old, beating Rosie Casals along the way. Boshoff also made the quarterfinals in Paris on one occasion and won the U.S. Open doubles title with Kloss in 1976, beating Wade and Morozova in the final. She retired to attend university classes in South Africa. I spoke with Ilana Kloss about her in 1998/1999, and she said Linky was happily married and the mother of three sons. Boshoff, by the way, was immortalized in a Peanuts cartoon in the 1970s. About her, Snoopy said, "She's only person that I'm taller than," or something like that, as well as, "How can you not love someone with a name like Linky Boshoff?" Boshoff herself once lamented that she would have given her right arm to be 5-foot-4. I think she was like 5-1-and-a-half.
As for Kloss, she plugged along for several more years and posted some decent results. She is now president or head of World Team Tennis.
Greer Stevens suffered a massive knee injury playing World Team Tennis in 1978, but actually played her best tennis after coming back from that injury in 1979. She posted big wins over Chris Evert, Tracy Austin and others, won one or two big tournaments and then retired at the end of 1980 to marry and run a dairy farm in South Africa with her husband. It was good to see her playing the Legends events at Wimbledon recently.
Marise Kruger was a big puzzle to me. I thought she had a decent shot of making the top 10, but she up and quit the game without hardly a word. I'm assuming she must have returned to school. She was a sweet girl, with good results, but her shots didn't have a lot of pace, which would have hurt her in the long run.
Bridgitte Cuypers won a futures' tournament and also seemed to play some tight matches against a lot of people. But here again, she seemed to up and decide to retire in 1979 without much fanfare. The last I heard, she was living in Chicago, but that was sometime in the early 1980s.
I think Cuypers and Kruger may have won a French or Italian doubles title in 1977 or 78, but don't have any records at hand to check.
One other player worth mentioning is Yvonne Vermaak, who played well into the 1980s and actually reached the Wimbledon semifinals in 1983. Vermaak was a very steady player, but also very short like Boshoff. She finally retired
Unfortunately, because South Africa was prohibited from Fed Cup competition in the late 1970s/1980s, the ITF data base does not have records for Vermaak and Kruger. But they do have records on the others, and it's worth a perusal. Hope this helps.