Grace Mugabe's alleged assault victim has been offered money to drop charges against the Zimbabwean first lady, minority rights organisation AfriForum alleged on Thursday.
Speaking at a press briefing in Pretoria, Advocate Gerrie Nel said the money was offered to Gabriella Engels, 20, by a third party.
Nel was unable to clarify the amount of money offered or by whom.
Engels, a full-time model, laid criminal charges against Mugabe on Monday after the 52-year-old allegedly assaulted her in a Sandton Hotel on Sunday.
Nel, who launched a private prosecuting authority funded by AfriForum after leaving the National Prosecuting Authority (NPA) in January, announced on Thursday morning that the organisation would represent and assist Engels during Mugabe's prosecution.
Nel said he is concerned about the possibility of political interference during her prosecution.
Afriforum is willing to "fight this matter to the highest court", he said.
Engels also attended the press briefing, but AfriForum CEO Kallie Kriel said she would not be addressing the media. She was seen with a bandage on her forehead where Mugabe allegedly hit her with an electric plug.
Police Minister Fikile Mbalula previously said Mugabe was expected to appear in court on Tuesday, but on Wednesday the police ministry said she never handed herself over to police.
"The suspect remains in South Africa," the police ministry said in a statement on Wednesday afternoon. Mugabe invoked diplomatic immunity to avoid prosecution, the ministry said.
According to South African legislation, Mugabe can only be granted immunity if her visit to South Africa was Gazetted by the Department of International Relations and Co-operation (Dirco) in advance.
The Police ministry said Grace Mugabe is expected to attend a Southern African Development Community (SADC) meeting underway in Pretoria, as well as attend to "personal matters".