As a federal court prepares to rule on a challenge to Sirhan Sirhan's conviction in the Robert F. Kennedy assassination, a long overlooked witness to the murder is telling her story: She heard two guns firing during the 1968 shooting and authorities altered her account of the crime.

Nina Rhodes-Hughes wants the world to know that, despite what history says, Sirhan was not the only gunman firing shots when Senator Kennedy was murdered a few feet away from her at a Los Angeles hotel.

"What has to come out is that there was another shooter to my right," Rhodes-Hughes said in an exclusive interview with CNN. "The truth has got to be told. No more cover-ups."

Her voice at times becoming emotional, Rhodes-Hughes described for CNN various details of the assassination, her long frustration with the official reporting of her account and her reasons for speaking out: "I think to assist me in healing -- although you're never 100% healed from that. But more important to bring justice."

"For me it's hopeful and sad that it's only coming out now instead of before -- but at least now instead of never," Rhodes-Hughes told CNN by phone from her home near Vancouver, Canada.

Sirhan, the only person arrested, tried and convicted in the shooting of Kennedy and five other people, is serving a life sentence at Pleasant Valley State Prison in Coalinga, California.

RFK assassination witness tells CNN: There was a second shooter - CNN