Isabel dos Santos, Angola's billionaire businesswoman and daughter of the former president, has launched a head-on attack on the government since her assets were frozen last month by graft investigators. Usually wary of the media limelight, Dos Santos has fired a broadside of scathing tweets, interviews and statements, lashing what she says are lies and a corrupt regime.The 46-year-old has been named "Africa's richest woman" by Forbes magazine, which last year rated her net worth at $2.2 billion.Among Angolans, her nickname is The Princess, denoting the wealth and status she accumulated in the oil-rich state during her father's 38-year rule.On December 23, prosecutors froze the bank accounts and holdings owned by Dos Santos and her Congolese husband Sindika Dokolo.She has denied any wrongdoing, variously calling the accusations "lies," "fake news" and "politically motivated".The investigation centres on alleged use of state-owned companies to siphon off over a billion dollars.It is delving into alleged irregularities involving the national oil giant Sonangol and Sodiam, a national diamond-marketing firm.Dos Santos was appointed head of Angola's national oil company Sonangol in 2016 - an act that for many critics exemplified nepotism under her father Jose Eduardo, 77.But she was forced out by his successor, Joao Lourenco, within months of coming to power in 2017.She has since left Angola, claiming she faced death threats after her father stepped down. She now lives in Europe, where she went to school and university.A judicial source told AFP Dos Santos would be formally charged in March, and her assets had been frozen as a "precautionary measure" while investigations were underway. - Impact on businesses? -Dos Santos has warned that freezing her assets would impact business she owns in Angola."My companies employ thousands of employees in Angola, providing well-paid jobs with good benefits," she tweeted. "We provide over 20 000 jobs, and we support over 30 000 small businesses."Dos Santos has holdings in two private banks, including the leading Banco de Formento Angola, the mobile operator Unitel, a supermarket chain and cable television.Those threats were brushed off by government officials, unions and economists.Angolan economic expert Carlos Rosado said that only Dos Santos' "personal bank accounts" had been frozen."Workers do not (directly) depend on Isabel dos Santos to pay them wages," Rosado told AFP.He added that most of the companies in which Dos Santos owns stakes would "continue to operate"."This case is about the repatriation of capital and the government will continue," External Relations Minister Manuel Augusto said this week during a trip to Portugal, Angola's former colonial power."It is not an isolated case against Isabel dos Santos."'Desperation' In an interview with Voice of America (VOA), Dos Santos said the whole government system was corrupt and that she was concerned about the "rule of law"."I'm a just a businesswoman," dos Santos told VOA, distancing herself from politics. "The main reason I'm concerned is because this has a huge impact on many, many companies."The head of Angola's independent unions, Francisco Jacinto, said Dos Santos was playing an act of "desperation"."There will actually be no change in working relations and companies will not be affected," he told AFP.Lourenco has vowed to fight corruption and rebuild the economy of the second-largest oil producer in sub-Saharan Africa.Angola is still reeling from a 1975-2002 civil war and a legacy of poverty and cronyism under its former president.Despite extensive oil and mineral wealth, the majority of Angolans live in poverty and continue to rely on subsistence agriculture. Hand-picked by Dos Santos, Lourenco has launched a large-scale purge of his predecessor's administration, during which key positions were awarded to the ex-president's relatives and close allies.Isabel dos Santos is the former president's oldest child, the daughter from his first marriage with Russian-born Tatiana Kukanova, whom he met while studying in Azerbaijan.Dos Santos' son Jose Filomeno - nicknamed "Zenu" - went on trial last month for allegedly embezzling $500 million from Angola's sovereign fund, which he oversaw from 2013 to 2018.Zenu, who faces a maximum 12 years in jail, is the first member of the Dos Santos family to be prosecuted.Isabel dos Santos' half sister Welwitschia, who lives in Britain, was suspended from Angola's parliament in October for absenteeism and "unjust enrichment".This week she told AFP: "There is compelling evidence... of a political agenda and persecution... from President Joao Lourenco."