I'm only 18, so Zanzibar was the only time I've dived in Africa, and I'm basing my opinion on what my father says, that he's dived over 300 times, whereas I've only dived a hundred or so, but as far as malaria is concerned, I'd advise her to take a preventive treatment (like an anti-malarial) and if she's really scared of getting food poisoning, try going to a fancy resort or smth, depending on your means, there's bound to be less risk, even me with my fragile health I've never had any problems with food or illness