South Africans have even been known to buy expensive yachts in S.A., sail across the Atlantic to Rio and beyond, then sell them, but I hear they're on to that one too now.
The ones that do come into money outside the country have learned not to take it back in and make use of off-shore accounts, i.e Channel Islands, etc.,
I'm afraid that illustrates what a problem your Granny has. I have heard that Bright, and possibly even Echo, have traders in S.A., so the trading a/c aspect could be looked at, but one can only assume that door has been shut as well.
The only way would be for her to take the max allowed for trips out of the country, (vacation money),which I think has been substantially increased in the last few years, and slowly siphon it out that way. At least she could get some out that way.
Best of luck.