Today, in a Pennsylvania courtroom, she told her story publicly for the first time.
On at least one occasion, Constand said she rebuffed his advances, telling him she had no interest.
After the incident, Constand acknowledged under questioning from both sides that she maintained contact with Cosby but said she felt obligated to do so because of her job. Constand was considering a career change and went to Cosby's home to discuss it.
Leaving his home later, she said she did not initially report the alleged assault out of loyalty to the basketball team she managed, of which Cosby was a trustee. She said she became unconscious and when she awoke she was partially undressed and Cosby made her touch his genitals. She says she then felt paralyzed and helpless as Cosby groped her. The TV star once dubbed America's Dad could get 10 years in prison if convicted.
Andrea Constand, the former Temple University employee who has accused Bill Cosby of drugging and sexually assaulting her in 2004, testified for the second straight day at the Norristown, Pennsylvania, court. Constand knew he was well connected and said she felt humiliated and confused. Mr Cosby says he gave the woman Benadryl to relieve stress and insists their sexual relations were consensual.
Dozens of women have accused Cosby of sexual assaulting them, often after plying them with drugs, in a series of attacks dating to the 1960s.
Tuesday marked the first time Constand had faced each other in court since 2005, when she was given a financial settlement after she filed a civil suit against Cosby.
Tall and thin with big, frizzy hair, she approached the witness stand as Cosby sat at the defense table, leaning forward, listening.
Bill Cosby's chief accuser is back on the stand at his sexual assault trial, facing cross examination Wednesday.
"I wasn't able to", Constand said, answering Feden's questions why she didn't tell him to stop or to push him away. Her claims were supported with testimony by Johnson's mother and her former lawyer, who said they heard about the assault after it happened, and of Cosby's subsequent attempts to have her fired from the talent agency shortly after it occurred.
Phone records showed Constand called Cosby 53 times between January 20, 2004, days after the incident, and March 31, 2004, when she left Temple University, including twice on Valentine's Day. She is one of the many women to claim sexual assault by the entertainer.
Cosby appeared indifferent throughout much of Constand's testimony. Johnson testified on Monday that the alleged assault happened in 1996.
Johnson testified on Day One that she lost consciousness in 1996 soon after Cosby pressured her to take a large white pill.
Other details did match up. She also said she received another call in which her daughter claimed Cosby was pressuring her boss, the comedian's agent, to get rid of her.
"These will help you relax", she remembers Cosby saying.
"The man that I've known as a child was amusing and witty and smart and philanthropic and full of advice", she told ABC News. "A mentor", she said.
But Miller's timeline differed from Johnson's.