When it comes to short term car insurance, the choices are limited when you don't have a full UK driving licence or a European one and for any other countries, most insurers will not provide any cover at all.
There's just one company offering temp cover to those with driving licences from South Africa, Australia, USA, New Zealand, Canada and you'll get the information you need in the link below:
There are several reasons why there aren't many companies offering temporary insurance to foreign drivers but the most important is that legislation in other countries is different from that of UK/EU. If it was for an annual contract, then it would be different and a lot easier to acquire.
Is your daughter not able to extend her policy back in South Africa to allow her to drive your car here in the UK?