Campbell's former agent, Carole White, testified Tuesday that she witnessed the model telling the head of a charity that the diamonds she was donating were a gift from Taylor.
But last week, the model testified she did not know the source or value of the "stones," claiming two men came to her room in the middle of the night and said merely it was "a gift for you." The British supermodel said she did not even know they were diamonds.
On Tuesday, Taylor's lawyer Courtenay Griffiths accused White of lying to help her case against her former client, whom she is suing for millions of dollars for alleged breach of contract.
White said her testimony is true and not about money.
On Monday, actress Mia Farrow also contradicted Campbell's testimony. Farrow told the court that Campbell had told her the day after the 1997 dinner that she received "a huge diamond" from Taylor.
Taylor faces 11 counts of war crimes linked to allegations he supported rebels during Sierra Leone's brutal 11-year civil war, which ended in 2002 with an estimated 100,000 dead. Prosecutors accuse him of financing the rebels with blood diamonds. Taylor denies the charges.
The Associated Press contributed to this report.