Candace Smith told police in June that Carruth so strongly disliked Cherica Adams that he wished for her death, The Charlotte Observer and CNN/Sports Illustrated reported.
Smith also said Carruth told her in earlier conversations he should have someone "beat her up or kick her in the stomach and make her have a miscarriage."
The Observer reported that it had obtained a copy of the 32-page transcript of Smith's interview with police. CNN/SI did not divulge the source on which it based its report.
Carruth and three other men have been charged with plotting Adams' murder. Prosecutors have accused Carruth of masterminding the slaying because he didn't want to pay child support.
Carruth, who could face the death penalty if convicted, maintains his innocence.
Smith is expected to testify in Carruth's capital murder trial, which begins a second week of jury selection Monday.
Lead prosecutor Gentry Caudill told The Associated Press he would not comment on the story, the content of the transcript or the effect it might have on the trial.
Defense lawyer David Rudolf did not immediately return calls Sunday seeking comment.
Rudolf told The Observer that nothing in the newspaper's story attributed to Smith is true. The account also differs from the first statement she gave to police in November, Rudolf said, according to the newspaper.
According to the published reports, Smith joined Carruth at Carolinas Medical Center just after the drive-by shooting as doctors struggled to keep Adams and her baby alive. Adams, 24, died a month later, but doctors saved the baby.
She said she spoke to Carruth after a police officer finished talking to him at the hospital. Smith quoted Carruth as saying: "I was in front of her and I slowed down and hit the brakes just enough for her to slow her car down, and that's when I saw the dudes come up and fire into her car."
Smith said she asked Carruth what he did after he witnessed the shooting.
"He was like, I just drove off ... ," Smith said.
Defense lawyers have said Carruth supported Adams financially during her pregnancy and attended medical appointments and a childbirth class with her.
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