Finding someone in South Africa is not so different to finding someone in the United States. Now that phone directories and other official records are available online, you can do most of your searching from the comfort of your own home. As with any type of people search, the more information you have about the person the better. At a minimum, you'll need your relative's full name, but a city or last-known address can make the search significantly easier.
South Africa White Pages
The South African White Pages contains telephone number listings for subscribers across the whole of South Africa. Search the directory by typing in your relative's full name. Narrow the results by location if you know roughly where your relative lives; without this filter, you may end up with hundreds of potential matches to sift through. If the person is listed, a free search should turn up her current address and telephone number, plus a map of her location.
South Africa Reunion Website
SA People Connect, an online reunion website, is geared towards reuniting people who are living, or who formerly lived, in South Africa. The site contains records for over 800,000 people. Register an account for free using the sign-up form on the website. Once registered, you can search for South Africans by name anywhere in the world. There's an active forum where you can post a notice about the relative you are looking for, or search the extensive database of school, university and army records. Basic searches are free but you'll have to pay for advanced searching and photo uploads – see the website for details.
South African Electoral Rolls
Every citizen over the voting age is eligible for registration on the South African electoral roll, which currently contains around 20 million names. You'll need to travel to South Africa to inspect the roll or have someone you know do so at the Municipal Electoral Office. Another option is Ancestry.com. This website maintains a database of South African voter indexes from 1719 to 1996 which you can search online to see if your relative is listed. Obviously, the information is not up to date. Since the search will take only a couple of minutes, however, it's worth a try, and it may turn up an address where your relative is still living.
Google and Social Media
Around 16 million people or 30 percent of the South African population use Facebook, so it's worth searching to see if your relative has a profile. After typing your relative's name into the search bar at the top of the page, use the location filter to narrow down your search results to include only people in South Africa. It's also worth typing your relative's name into Google or another search engine if you haven't done so already. If your lost relative has left her name on websites or has done anything newsworthy, the chances are good that Google will display those results for you. This may give you some clues as to her location.
Hire an Investigation Agency
An international or South-Africa based investigation like Intertel can trace the current residence and whereabouts of the relative you're looking for. You'll need to give the agency enough information to locate the lost relative, such as a South African Identity Number, actual or approximate date of birth or last-known address. The more information you provide, the better the chances of tracing the correct individual. Some agencies operate a no-trace, no-charge fee structure; others charge a flat fee regardless of success. Be sure to understand the scope and cost of the service before you sign up.