"Dynamic" is a description bestowed by Shell communications head Lutz Kranz. Liefferink has battled alone against the fuel giant's plans to build a Shell Ultra City in the centre of a residential area.
She emerged victorious on Tuesday evening. That was when Shell informed her it was abandoning its plans, as it "dearly" wanted to consider the will and health of ordinary people.
Kranz added: "She is an example of the power that lies within the individual."
Liefferink said on Wednesday that her triumph was proof that "the voice of small, insignificant people without titles or unusual training has enormous power".
"The credit should not go to me. I was fighting for the community."
Liefferink's battle started in 1995 when Shell lodged an application with the city council to build a filling station a stone's throw from her home.
Up until Tuesday evening, when she was officially told Shell had abandoned its plans, she and her family had been subjected to large-scale intimidation, lies and attempts at bribery.
Shell had repeatedly informed her that her "activist actions" were costing it millions of rand, and advised her to stop them.
"I can now say that I remained incorruptible. I never accepted any bribery gifts."
The battle has cost her at least R100 000. However, in the process, her knowledge of the law has greatly expanded.
Liefferink said: "It (the petrol station) would not only have had a detrimental effect on property values, it would have exposed us to petrol fumes, noise and dust. Life would have become unbearable."
The entire neighbourhood had initially voiced its objection to the envisaged development. The others lost interest, however, as time passed.
Liefferink persevered. She started to consult the law books of her father, former magistrate FWP Maritz, and bought more law books. "I now have an entire law library. I have decided that the people have to be informed."
She wanted to prevent it from being said, afterwards, "when it is already too late": "But we didn't know."
She typed up information brochures and had them printed at her own expense. She and two gardeners walked from house to house on Saturdays and Sundays, distributing pamphlets.
"Think about your children." She tried to incite the community. They never opposed her, but neither did they actively support her.
Several attorneys whom she asked for help, discouraged her and said she was fighting a losing battle against the fuel giant.
"I would just burst into tears from pure exhaustion sometimes. I was disheartened, but something inside me said: 'Mariette, you have to continue'. "
Husband Eric's support gave her momentum. She wrote letters day and night, and succeeded in getting the sympathetic ear of Gauteng environmental affairs and tourism MEC Dr Trish Hanekom.
Suddenly, after years, people starting listening to her. "It was wonderful. People no longer ignored my calls. They even started returning them."
She approached groundWork, a non-governmental organisation, about a year ago for help.
The organisation helped her with advice, and invited her to take part in a panel discussion at the pre-summit of the World Summit for Sustainable Development. "I had to relate my battle against Shell."
She told Shell about the invitation. Kranz faxed a letter to her the next day in which he said Shell had decided to abandon its plans. "I am relieved. Now I can continue with my life," she said.
Environmental organisations by common consent launched an Internet war against Shell's worldwide activities on Wednesday at the pre-summit of the Earth Summit in Sandton.
They have created a website where victims of Shell's activities can share their stories with the rest of the world.
The address is www.shellfacts.com and the stories will be chronicled later this year.