If you invest in your nanny she will probably invest in you and you don't have to invest money, just time. Treat her in the same way that you expect to be treated at work and chances are you will recieve a reciprocal loyalty to your family. Spend at least 10 min a day finding out about how things are going rather than beings ships that pass in the doorway when you're on your way out and she's on her way in (and vice versa). Think about how soul destroying it must be to work in a place where there is no guidance and direction and then when things go wrong there are rants & raves.
Train her - if you can't afford to send her on a course or two, take an hour out a month and show her something new - your cultural point of reference is likely to be totally different to hers. She will feel she is really making a difference if she is doing something with your child that you want her to rather than guessing her way through the day.
If you can't send her on a course, teach her first aid and emergency procedures so that she's confident she can deal with your child if there's a problem.
Teach her to cook what you would like her to feed your child rather than assuming she knows how. Most people want to please and they can only please you if you've let them know what you like.
Be considerate but firm in understanding her family responsibilities - in the same way you would want your employer to treat you although you need to give some kind of leeway - 3 days of family responsibility leave doesn't go very far when it takes 3 days to travel there and back.
Relationships are give and take and a lot of people don't "give" (and I'm not talking in the material sense) to their nannies / domestic workers. A bit of s risk I'd say when they're looking after your precious ones.
There will always be the one that doesn't come back from leave - but this is not a domestic worker thing - it's a human nature thing, in the same way that people in a commercial environment don't give notice to their employer and just leave but the better the relationship the harder it is to do that kind of thing.
And then also consider that someone in the Eastern Cape is probably supporting an extended family so their problems may be bigger than you perceive and if something has happened that there is no-one to look after THEIR child, they just may not have an option but to stay there. In which case limit your losses and employ someone closer to where you live.
I know how you feel, I've been in your space but when I looked at the problem behind the problem I figured I needed to do some changing too. Good Luck.