Johannesburg - Representatives of Zimbabwe's first lady say a young woman who accused her of assault was the actual aggressor, allegedly attacking Grace Mugabe with a knife while drunk, according to a court document filed in South Africa.The court papers denying any wrongdoing by Mugabe were submitted on August 17 by Zimbabwean diplomats on behalf of Mugabe, who was granted diplomatic immunity by South Africa despite calls for her prosecution in the alleged attack on the woman in a Johannesburg hotel on August 13. She returned to Zimbabwe a week after the alleged assault with President Robert Mugabe, who had attended a summit of southern African leaders in Pretoria.The Associated Press obtained a copy of the court document on Tuesday from AfriForum, a group representing 20-year-old Gabriella Engels, who said she suffered head wounds while being whipped with an extension cord by 52-year-old Grace Mugabe. AfriForum has said it will challenge the South African government over the immunity issue in an attempt to complicate any effort by the first lady to return to South Africa.Grace Mugabe went to see her sons in a hotel suite because they were "in trouble with a drunken young woman", says the court document filed by Zimbabwean diplomats."Upon her arrival Ms Engels, who was intoxicated, and unhinged, attacked Dr Grace Mugabe with a knife after she was asked to leave the hotel room. Security was left with no other option but to remove Ms. Engels from the hotel suite," according to the court filing.Mugabe "reserves the right to press charges of attempted murder" against Engels, the document says.Engels has said she was in a hotel room with mutual friends of Mugabe's two sons, who live in Johannesburg, when the first lady burst into the room and assaulted her. Photos posted on social media show a bloody gash to Engels' forehead that she claims was a result of the encounter.In 2009, a photographer accused Mugabe of beating him up in Hong Kong. While the Zimbabwean president's outspoken wife has been criticized for a fiery temper and lavish shopping expeditions, her rising political profile has some asking whether she is maneuvering to succeed her husband. She recently said that Zimbabwe's ruling party should restore a constitutional provision stating one of the party's vice presidents should be a woman, and has publicly challenged her 93-year-old husband to name a successor.