Investigators in Mumbai linked Headley to the woman through a suitcase that he left behind, according to a report in Wednesday's Indian Express newspaper.
The Parsi woman is said to have been employed as a "kitchen executive" at the Oberoi Trident Hotel, one of the main targets of al-Qaeda-connected Pakistani rebel commandos during a deadly assault in November of 2008. 165 people ended up dead in the attacks including six Americans; attacks that Chicagoan David Headley is accused of helping to plan and plot.
Unnamed Intelligence sources quoted by The Indian Express said that Headley's girlfriend was cooperating and has provided key leads in the ongoing investigation.
The woman, a hotel management graduate whose name is being withheld, has reportedly told investigators that she frequently dined with Headley at other Mumbai targets as well including the Taj Hotel and the Leopold Café which ended up under attack by terrorist grenades and gunfire.
Headley, 49, on Wednesday pleaded not guilty in Chicago to U.S. charges that he scouted targets for militant Pakistani terrorists.
After court, Headley's attorney John Theis called the accused terrorist a very intelligent man who is assisting in his own defense. Theis said the defense team is "still in the process of reviewing all of the evidence."
In court documents, prosecutors have revealed details of his alleged surveillance in India on behalf of Lashkar-e-Taiba and another militant group in planning the Mumbai attack and details of another plot against a Danish newspaper.
Denmark's Jyllands-Posten newspaper was targeted after publishing cartoons in 2005 depicting the Prophet Mohammad that offended many Muslims.
Headley, who was born in the United States but spent several years in Pakistan, has previously pleaded not guilty to similar charges.
His accused co-conspirator, 49-year-old Pakistani-born Chicago businessman Tahawwur Rana, entered a not-guilty plea on Monday to charges he provided material support to the plots and to Lashkar.
It is not clear if American investigators have spoken to Headley's one-time girlfriend in Mumbai. Headley's attorney declined to say whether he had been contacted by Indian authorities.
The Indian Express reported that Headley had "assiduously pursued" the Mumbai woman, courting her with flowers, email and text messages when he was abroad and last March with a gift of a platinum bracelet.
The newspaper reported of their relationship that: "Headley frequently spoke to her about his 'fascination' with close-combat weapons and admitted he had interactions with 'weapon mafia dons' during his frequent visits to Pakistan."
Headley left two of his suitcases and a fax machine in the girlfriend's home. On his last visit according to the Express report, he went to the house and picked up only one of the suitcases. The one he left behind, intelligence sources were reported to have said, contained used clothes, shoes, toiletries, tinned food, visiting cards, a copy of Headley's passport and registration papers of the Osho Ashram ? which Headley visited in July 2008 ? and a Nokia handset with a SIM card.
The cell phone address book contained a "list of international numbers, which are being analyzed. Investigators have also confirmed a 'Headley connection' with a male fashion designer (name being withheld) who runs a fashion store on Bhulabhai Desai Road and came in contact with Headley at the gym in early 2007."
Although federal prosecutors have said that Headley is assisting them in their investigation, Headley's lawyer declined to confirm?or comment?on any cooperation agreement.