The woman, operating under the codename Nomidia, used elaborate methods to evade capture -- constantly changing her location, using multiple mobile telephone SIM cards and hiding her activities from all but the closest members of her family.
Her biggest protection against arrest by Gaddafi's security forces though was her gender: as a young woman in Libya's conservative Muslim society, they did not suspect her.
"I was not on the radar," the woman, an engineer, told Reuters in an interview in the lobby of a Tripoli hotel, two weeks on from a rebellion that broke Gaddafi's control over the Libyan capital after 42 years in power.
"They were concentrating more on the guys and it was almost impossible to think that a girl was doing all of this."
Nomidia spoke to Reuters on condition that her real identity not be revealed: she said that while Tripoli was now under control of a new interim government, there was still a "fifth column" of Gaddafi loyalists who might target her or her family.
The account she gave of her activities was corroborated by two other people who were part of an underground anti-Gaddafi network and helped her send details about his security forces.
"(She was) a very important source, and very trusted," said Osama Layas, a forensic pathologist who was a member of the network.
In Tripoli now, crude caricatures of Gaddafi dressed as a woman are pasted on checkpoints. The billboards bearing his image have been defaced or ripped down.
When Nomidia began her undercover role five months ago, Gaddafi and his security forces had a firm grip on the city and stifled any information which could be useful to his opponents.
Telephone lines were monitored, mobile phone text messaging was blocked, and the internet was available only to government offices and a group of foreign journalists who were kept under guard in a five-star hotel.
The city's prisons were full of people suspected of aiding anti-Gaddafi rebels or even just of passing information to someone outside Libya.
A tall, slender woman with a green chiffon scarf draped over her head, Nomidia said she felt compelled to act after the brutal way in which Gaddafi's forces put down the first stirrings of revolt in cities around the country.
"I could not help it when I saw what Gaddafi did in Benghazi first, in Misrata, in Zawiyah, in Tripoli, the Western Mountains," she said.
She began by calling Libya al-Ahrar, an anti-Gaddafi television station based in Doha, Qatar. With little real information leaking out of Tripoli, producers at the station put her voice on air -- under the name Nomidia -- with accounts of what was happening in the city.
Soon she was dialling in with details of military forces which the channel wanted to keep off the air to avoid alerting Gaddafi's government.
Instead they began passing on the information to NATO, via officials with the rebel government, the National Transitional Council (NTC), said Lina, at the time a producer at the station who was Nomidia's principal point of contact.
With the telephone network under surveillance, the most dangerous part of Nomidia's activities was passing on information about the targets.
At one point, a businessman and member of the anti-Gaddafi network gave her a satellite phone to use, though this in itself was risky because the government had outlawed their use.
She also changed location frequently. "One day I called from Tajoura, one day from Souk al-Jumaa. Different places," she said, ticking off neighbourhoods in Tripoli.
NATO reconnoitered targets for its strikes using satellites and unmanned drones. But there were limits to this approach. In some cases, Gaddafi's forces set up concealed bases inside civilian buildings. Also, the alliance could not be sure there were not civilians at the targets.
That was where Nomidia, and others like her, came in.
"We have at least 16 guys working for us doing this. There was a woman who was giving us information," said Hisham Buhagiar, a senior NTC military official.
"This was a big operation with many small pieces. You could probably not have done it without any of them," he said.
A NATO spokesman said he could not reveal details about who had passed on information about targets in Tripoli and how, but he said they played a valuable role.
"Certainly any mission like this where we are trying to locate and strike, with pinpoint accuracy, weapons...we rely heavily on intelligence and surveillance," the spokesman said. "It is pretty clear that we used these sources of information well."
In her interview with Reuters, Nomidia named three sites she said had been hit by NATO after she had provided information.
They were a site in the Salaheddin district of Tripoli, formerly used by a Turkish company, where pro-Gaddafi militias were storing weapons; the April 7 military camp in the Bawabit Al-Jibs neighbourhood; and an intelligence service building in the Sidi El-Masri district.
"The information about these sites was coming from highly ranked army officers who were not with the regime. They were supporting the revolution. My father also is a retired officer, so he was cooperating with friends and even family (who were in the military)," she said.
"The Gaddafi regime was using civilian sites to store weapons ... I was driving my car, by myself, and went directly to the site and monitored the site, observing the site, for maybe hours, to make sure it should be struck," said Nomidia.
As rebels fought their way into the capital, the NTC said Saif al-Islam, one of Muammar Gaddafi's sons, had been captured. That was shown to be wrong hours later when Saif al-Islam appeared at the hotel housing the foreign media.
Nomidia already knew the reports were untrue because, she said, she had a source inside the operations room in Bab Al-Aziziyah, the compound in Tripoli from where Gaddafi's security services were directed.
"She got the information from inside Bab al-Aziziyah. She had a contact there. And it turned out to be true. After half an hour, Saif was on CNN."
Two months earlier, she had come close to being caught. She found out from her contacts that Gaddafi's security forces had tracked one of the SIM cards she was using, and knew her real first name, though not her family name.
"So I turned off all my mobiles and I kept moving, as well as the whole family, from house to house, just to be safe," she said. "That was the most difficult situation."
She described her contribution to undermining Gaddafi's rule in a matter-of-fact way and had to be prompted to reflect on what had been at stake.
"I was expecting I might be arrested at any moment. That was on my mind all the time," she said.
But she added: "I wasn't scared at all ... I was very optimistic that I would succeed. That everybody would succeed. I thank Allah that I'm alive to see the result of the job that I did and others did."
(Additional reporting by Mohammed Abbas in Tripoli; Editing by Louise Ireland)