Zaziwe Manaway told CNN Mandela wants people to stop spreading rumors on social media that he has gone home to die.
Manaway described Mandela, who celebrated his 94th birthday in July, as an alert man who still reads the newspaper every morning and enjoys playing with his grandchildren.
"It can be very, very hurtful for us to hear these messages out there in the social media that our grandfather is going to go home to die. It is insensitive," she said.
Given his age, Mandela's need for medical treatment is to be expected, Manaway said.
Mandela has kept out of the public eye since 2010. His last public appearance was at the World Cup in South Africa.