Visa Extension ? (Johannesburg)

Hello, Can anyone give me some advice - can tourists extend their visitors Visa?

I am working here as a consultant, and my gf is staying with me and wants to stay a few weeks longer.

She's already been here for 11 weeks and here visa is up soon.

I have been told she needs to go all the way home to Canada... before returning - but she has family in Kenya - any idea if she can Visa run?

Any help suggestion would be welcome

Thanks
Andrew