The fever tree / Jennifer McVeigh.

Enhanced descriptions from Syndetics:

Having drawn comparisons to Gone with the Wind and Out of Africa , The Fever Tree is a page-turner of the very first order.
In London she was caged by society.
In South Africa, she is dangerously free.

Frances Irvine, left destitute in the wake of her father's sudden death, has been forced to abandon her life of wealth and privilege in London and emigrate to the Southern Cape of Africa. 1880 South Africa is a country torn apart by greed. In this remote and inhospitable land she becomes entangled with two very different men--one driven by ambition, the other by his ideals. Only when the rumor of a smallpox epidemic takes her into the dark heart of the diamond mines does she see her path to happiness.

But this is a ruthless world of avarice and exploitation, where the spoils of the rich come at a terrible human cost and powerful men will go to any lengths to keep the mines in operation. Removed from civilization and disillusioned by her isolation, Frances must choose between passion and integrity, a decision that has devastating consequences.

The Fever Tree is a compelling portrait of colonial South Africa, its raw beauty and deprivation alive in equal measure. But above all it is a love story about how--just when we need it most--fear can blind us to the truth.