Forrester said: "This is the kind of offence that cannot be tolerated in our society.
"I can't think of another case in 25 years that there's been so much obstruction of justice."
The conspiracy was foiled after Pepsi warned Coca-Cola it had received a letter in May 2006 offering Coca-Cola trade secrets to the "highest bidder".
The FBI launched an undercover investigation and discovered that the letter was written by Ibrahim Dimson, Williams's co-defendant who was jailed for five years on Wednesday.
A third defendant, Edmund Duhaney, will be sentenced later.
Williams stole confidential documents and samples of products that had not been launched from Coca-Cola and gave them to the two other defendants, the court was told during the trial.
During the trial, prosecutors introduced surveillance video showing Williams packing documents into a bag at her office.
They also produced phone records showing calls made from Dimson's number to Williams shortly after he had spoken to an undercover agent, who posed as a third party, on expressing an interest in the documents on behalf of Pepsi.
Duhaney testified that Williams, a family friend, had initiated the plan and provided confidential documents and samples of unreleased products.
"This case is an example of good corporate citizenship leading to a successful prosecution," David Nahmaias, an Atlanta-based US lawyer, said in a statement, referring to PepsiCo's co-operation with its leading rival.
"Unlawfully gaining a competitive advantage by stealing another's trade secrets can lead straight to federal prison," he said.