Compass Collective spokeswoman Katia Tempel told the BBC that rescuers aboard the Trotamar III found the young Sierra Leonean migrant wearing a simple life jacket and two waist cameras around 03:20 (02:20 GMT) on Wednesday. .
The girl told them that the metal boat she was on sank in seconds due to a strong storm with waves 3.5 meters (11.5 feet) high, and that she and two other people had been in the water for some time, but then they lost contact.
Rescuers handed her over to Italian authorities on the island of Lampedusa, where she could walk and talk.
The International Organization for Migration (IOM) says 30,955 migrants have died or are missing crossing the Mediterranean since it began recording the numbers 10 years ago.
According to data published by the UN refugee agency, UNHCR, Italy has taken in more than 63,000 people this year alone.
However, the numbers fell in part due to the hard-line policies of Prime Minister Giorgia Meloni’s right-wing Italian government.
