The 22-year-old was visiting a camp run by Kevin Richardson at the Dinokeng Game Reserve in Gauteng, near Johannesburg, when she was attacked on Tuesday morning.
She had been accompanying a friend for an interview with the manager of the camp, and the pair were taking photos as they prepared to leave before the lioness encountered her.
It had been pursing an impala at the “Big Five” reserve, which is home to lions, leopards, elephants, rhinos and buffalo.
Mr Richardson, who has appeared in several documentaries and films as a result of the relationships he has developed with big cats and hyenas, said he was “saddened and shocked” to hear of the incident.
“Myself and an experienced colleague took three lions walking in the reserve, as we do on a weekly basis, as part of their exercise and stimulation regiment,” he explained.
“We assessed the landscape for other Big Five animals and as per procedure sent out a notification that we were walking in the reserve.
“One of the lionesses charged off after an impala and must have run 2 to 2.5km, where she encountered the 22-year-old outside the car.
“I am devastated and my heart goes out to this young woman’s family.”
Paramedics were called at about 11am but the woman was pronounced dead at the scene.
She has not been identified but is believed to be South African, according to local media.
Fans of Mr Richardson and the reserve have shown their support for his work on social media, with many expressing hope that the animal would not be euthanised.
In 2015, Mr Richardson defended a decision by The Lion Park – another reserve near Johannesburg – to spare the life of a lioness who mauled a tourist through an open window of a car she was travelling in.
He said it would have been unfair to put it down because the animal acted instinctively, and it was instead moved to an enclosure not accessible by visitors.
Dinokeng Game Reserve has 13 predator enclosures and a large central area in which the animals are rotated through every few weeks, with several camping options for those who wish to visit.