She is also claiming that Clark was duped into cutting her from the trial by a friend of Simpson who didn't want to see his friend go to jail.
Shively had just left her Brentwood apartment on the night of June 12, 1994 and was was rushing to the local market before it closed at 11pm when a white Ford Bronco suddenly ran through a red light with no lights on and swerved onto the median.
She locked eyes with the person who had nearly killed he as soon as their car came to a stop, and at first thought it was Marcus Allen.
She then realized it was Simpson, recognisinng him from his appearance in the recent film Naked Gun 33⅓.
"Everything happened so fast," said Shively.
"First I felt fear, then anger. I mean, the self-entitlement! Why was this person driving like this? They had to be drunk."
It was not until the next day that Shively learned what had happened just a few blocks away at Brown's home, with her sighting now the crucial piece of evidence in the investigation.
Shively quickly became the Simpson trial's all-star witness after helping the prosecution get their indictments of Simpson from the grand jury that July thanks to her very specific timeline of events from the evening and eyewitness account.
This was boosted in a big way by the fact that she had been rushing to get to the store before closing, and well aware of the exact time at all moments of that drive.
Things soon fell apart however when she agreed to do a paid interview with Hard Copy for $5000, a offer that proved too good to resist.
"I thought I would make some extra money and go on a vacation," explained Shively.
It also earned her the ire of Clark however, and a dismissal from the prosecution's witness list for the trial of the century.
She said that she received a call from Clark asking her to come down and speak with her, and things did not go very well.
"Marcia freaked out at me and said I blew her case" said Shively.
"She said, 'I was counting on you for my timeline, and you blew it.'"
Shively was then summarily dismissed at the end of that meeting and told her services were no longer required by Clark.
"I don't need her. I have enough evidence," Clark told the two lead investigators on the case and her boss Gil Garcetti claims Shively, who was still in the room at the time.
Clark, who Shively called "terrible" on Facebook recently, said in her book Without a Doubt that she began to question her star witness' strengths after being told she had duped actor Brian Patrick Clarke into pitching her plagiarized script to a production company.
Shively claims however that it was Clarke who got duped in the end.
"He made up things to discredit me," claims Shively, who said that Clarke was a softball buddy of Simpson who did not want his friend to go to jail.
She also said that she and Clarke eventually settled out of court.
The attention eventually became too much however for Shively, who said she felt "betrayed" by Clark for the way she was just dropped, with many stating in retrospect she could have done nothing but help the case for the prosecution.
"There was no safe zone. I lost my job. I remember putting my daughter to bed, and a guy was looking through her window with a camera. It was horrible,' said Shively.
"I would get people coming up to me saying I was "part of the white conspiracy." I'd get phone calls, people camping out outside my door. We hid out at some friends' houses for a while."
And the worst part is that she believes there is a chance Simpson would be in prison for good had she been able to testify.
"I may have made a mistake, but I didn't kill the case," said Shively.
"I realize now that all that stuff Marcia did to me was just horrible. They idolise her so much. I just don't understand."
