The star was celebrating his directorial debut, "The Gardener of Eden", at the now-shuttered Butter lounge in Manhattan, New York when, according to Cox, he led her "down a hall" to a VIP lounge area and assaulted her.
The woman, who now works as a therapist for children, described Connolly as being "friendly and mildly flirtatious" while working with him, but said she "laughed it off" at the time.
Speaking to The Daily Beast, however, she recalled the alleged incident, which took place at the bash, prior to which Cox and her team - headed by costume designer Amy Westcott - had been out for a private dinner.
"We were at the party and I don't think I'd been there for more than an hour or so when Kevin approached me and asked if I'd go with him for a smoke."
"As soon as we were alone in that area, he started to kiss me," she shared. "I didn't know how to respond - but before I could even think about what to do about it, he pulled me into one of those little side (booths), and pulled down my pants, and turned me around, and within no time was inside of me. I was just in shock."
The actor/filmmaker apparently threw a pillow at Cox after he finished, and proceeded to tell her to "clean" herself up before she attempted to re-enter the party, when she caught the eye of Westcott in the hallway, and her pal pulled her aside.
"Amy was immediately enraged and protective, and then went after (Connolly). Then they had an argument in the middle of the party, yelling at each other," Cox shared. "Amy said, 'Let's get you home,' and put me in a cab."
In emails obtained by the publication between Cox and Westcott, the costume designer states she "knew it wasn't consensual, and went after him," and tells Cox, "I thought you're (sic) ability to consent was impaired by alcohol" - despite Connolly alleging that Cox "was not extremely inebriated."
Connolly, who has not been charged in the alleged attack, "categorically denied" assaulting Cox while admitting a "lack of professionalism" on his part in connection to the encounter, in a statement issued by his attorney.
"Kevin completely understands Amy's displeasure with the consensual act that transpired between Kevin and Gracie 15 years ago, after production had wrapped and they were no longer working together on the movie," attorney Marty Singer said in a statement to The Daily Beast. "Kevin acknowledges the lack of professionalism on his part, but her adamantly denies that it was anything other than a mutual consensual encounter."
Cox said she regrets not getting a rape kit done after the alleged assault, and insisted, "I want it to be known that he is dangerous and I want him to not get away with it any longer."