Former Cosatu general secretary Zwelinzima Vavi and EFF leader Julius Malema are plotting to overthr.
Ngema-Zuma, whose mother lived with diabetes for more than 20 years, was speaking at Mercy Clinic in Winterveldt, where she donated a R1.2-million mobile clinic, which will now be permanently based there.
She said diabetes should not be seen as a killer disease when people are aware of it and know what to do. The mobile clinic has screened more than 45000 people since it was launched in 2007. Pharmaceutical company Novo Nordisk donated the clinic to Ngema-Zuma's foundation, who chose to give it to Mercy Clinic.
The clinic will now be a permanent place for treatment of diabetes and other incommunicable deceases.
Ngema-Zuma previously visited the clinic in 2010 to promote public awareness and education in diabetes.
"People in this community go all out to do better things for themselves," Ngema-Zuma said. "I have never seen such collaboration between the general public and a clinic, and it showed that when people work together they can achieve more.
"The way they wanted to make a difference for themselves showed me that they do not always want to depend but just need someone to hold their hand ... and I thought I could do my bit.
"I have no doubt that you will appreciate and guard it and make sure that its existence is of a lasting benefit to the community."
About 370-million people live with diabetes worldwide, and an estimated 6.5-million are South Africans.
Novo Nordisk's general manager Timmy Kedijang said the problem was that 50% of people living with diabetes did not know that they were suffering from the decease.