Mrs Bettencourt, who is at the centre of a corruption investigation that has involving Nicolas Sarkozy, the former French president, sold the islands to a Seychelles-registered conservation business linked to the Swiss Save our Seas foundation, which intends to turn it into a nature reserve, for £60 million – a profit of £42 million from when she first bought it.
Mrs Bettencourt is said to have handed over envelopes stuffed with cash to the former President of France.
In turn, the 89-year-old is said to have received massive tax breaks when Mr Sarkozy came to power in 2007.
Mrs Bettencourt has some £80 million worth of money in 12 bank accounts in Switzerland and Singapore.
D’Arros Island, together with a number of neighbouring private islets, was also in her portfolio, with Mrs Bettencourt admitting that no tax had been paid on their £18 million purchase price.
Now she has sold them for £60 million, she has agreed to pay some £8 million of unpaid taxes to the Seychelles government as part of the sale.
As well as the unpaid charges dating back to 1998, she also agreed to pay some £10 million in tax on the latest sale.
Despite the serious allegations levelled against her, Mrs Bettencourt has not faced any criminal charges.
The massive profit she has just made on Arros will lead to greater pressure on Mr Sarkozy, whose Paris home was raided by police a month ago, together with two offices linked to him.
Mr Sarkozy and his third wife, the former supermodel Carla Bruni-Sarkozy, were on holiday in Canada when detectives arrived, and have not been seen since.
Judge Jean-Michel Gentil believes that Mrs Bettencourt may have illegally contributed two payments of 400,000 euros (£335,000) each to Sarkozy’s 2007 election campaign.
Both were traced to Swiss accounts, and one was allegedly received by Mr Sarkozy in person in Paris.
Mr Sarkozy is also facing allegations that he profited from illegal arms sales to Pakistan, and that he accepted millions from former Libyan dictator Muammar Gaddafi.
Mr Sarkozy denies all the charges, with his lawyer Thierry Herzog saying the searches of his home and two lawyers offices linked to him would “find nothing”.