The woman -- using the pseudonym Sonia -- said she had received little support from the state in changing her identity and was living in fear, even though she had police protection.
Sonia was a friend of Hasna Aitboulahcen, Abaaoud's cousin, who helped him hide after he and a group of jihadists attacked Parisian cafes, restaurants, a concert hall and the Stade de France stadium on November 13, killing 130.
Sonia said she called police as Abaaoud revealed he was planning more attacks against a shopping centre, police station and a creche in Paris' La Defense business district.
"In my head I said they will not do it because I am going to stop them," said Sonia.
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Sonia said she was with Aitboulahcen, 26, on November 15 when she received a call from a Belgian number telling her to pick up Abaaoud, who was hiding in bushes near a motorway.
Sonia said she asked him: "Did you take part in what happened on November 13?
"He said, just like that: 'The terraces, that was me'," she said, in an apparent reference to the attacks on people sitting outside pavement-front eateries.
Investigators have said Abaaoud, a Belgian of Moroccan origin, was part of a team of gunmen who drove around the east of Paris spraying roadside cafes and restaurants with bullets.
"I said: 'But you killed people, you killed innocent people'," said Sonia.
"He said: 'No they're not innocent. You must see what's happening to us in Syria.'