The discovery, confirmed to AFP by the Italian coastguard, brings to seven the final death toll in the sinking of the "Bayesian", which went down off the Italian island before dawn on Monday.
Italian media reported earlier on Friday that the body had been identified as 18-year-old Hannah Lynch.
The bodies of Mike Lynch, a celebrated tech entrepreneur and investor, and four other passengers were found on Wednesday and Thursday, with Hannah the only one still missing.
Emergency services had found the body of another man, believed to be the yacht's chef, a few hours after it sank in a sudden storm.
Lynch had invited friends and family onto the sailing boat to celebrate his recent acquittal in a massive US fraud case.
But as the 56-metre (185-feet) British-flagged yacht was anchored off Porticello, near Palermo, it was struck by a waterspout - akin to a mini-tornado.
It sank within minutes.
Italian authorities launched what they called a "delicate" search operation involving specialist divers, boats from several emergency services and helicopters.
'Heartbroken'
Fifteen people had been rescued from the ship, including Lynch's wife, who is believed to have been waiting in a Sicily hotel for news of her husband and daughter.
Hannah had just finished her end of school exams and had a place to study English literature at Oxford University, according to UK media reports.
Friends of the teenager told The Times newspaper that she was kind and clever, as well as a staunch feminist.
The bodies of Lynch's lawyer Christopher Morvillo and his wife Neda, and Jonathan Bloomer, the chair of Morgan Stanley International, and his wife Judy, were recovered on Wednesday.
Morvillo's firm Clifford Chance paid tribute to the lawyer and his wife, saying all were "heartbroken at the tragic passing... and still coming to terms with this terrible loss".
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The Bloomer family described their "unimaginable grief", saying Jonathan and Judy had been together for five decades.
"Our only comfort is that they are still together now," the family said.
The Lynch family has yet to comment publicly.
Many questions remain about why the yacht sank, and so quickly, when other boats nearby were unaffected.
On Thursday the head of the company which built the boat said the tragedy could have been avoided.
"Everything that was done reveals a very long summation of errors," said Giovanni Costantino, head of the Italian Sea Group, which includes the Perini Navi company that built Bayesian in 2008.
Bad weather forecast
He told Italy's Corriere della Sera newspaper that bad weather was forecast and all the passengers should have been gathered at a pre-arranged assembly point, with all the doors and hatches closed.
"Instead it took on water with the guests still in the cabin. They ended up in a trap, those poor people ended up like mice in a trap," he said.
Lynch, 59, was acquitted on all charges in a San Francisco court in June after he was accused of an $11 billion fraud linked to the sale of his software firm Autonomy to Hewlett-Packard.
The Bayesian, owned by his family, boasted a 75-metre mast, the tallest aluminium sailing mast in the world, according to the Charter World website.
Raising it would likely cost some 15 million euros and take "six to eight weeks", according to the salvage engineer who led the operation to recover the Costa Concordia cruise ship, which sank off Italy in 2012.
To recover the yacht, the mast could be removed on the seabed but the boat would be lifted up whole using a giant crane and a team of 40 specialist divers, South African engineer Nick Sloane told the Repubblica daily.
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