In an interview with a leading US daily, she said that after dinner one night in 1991, they took her back to Simmons' apartment to show her a music video they had been working on.
But Simmons quickly began making aggressive sexual advances and tore off her clothes.
"I looked over at Brett and said 'help me' and I'll never forget the look on his face. In that moment, the realisation fell on me that they were in it together," noted Khalighi.
She said that Simmons then tried to force her to have intercourse, which she "fought wildly."
While taking a shower, she said, Simmons walked up behind her and briefly penetrated her without her consent. She jerked away and then he left, she said, saying of the experience, "it hurt so much."
Simmons denied the allegations in a statement on his website.
Simmons wrote, "I am a supporter of the #MeToo campaign and the victims who were previously terrified to stand up and speak out against sexual misconduct. I completely and unequivocally deny the horrendous allegations of non-consensual sex against me with every fibre of my being."
The statement continued, "I know Keri Claussen Khalighi and remember the weekend in 1991 that she has referenced. Everything that happened between us 26 years ago was completely consensual and with Keri's full participation. We spent time in my apartment over a period of two days and one night, as well as at some public places including Nell's Nightclub. I'm deeply saddened and truly shocked to learn of Keri's assertions as to what happened over the course of that weekend."
Ratner has been accused of misconduct by six women, including actresses Olivia Munn and Natasha Henstridge.
Ratner, meanwhile, via his attorney Martin Singer, has disputed the accounts of sexual misconduct he has faced from at least 10 other women. (ANI)