NEWARK, N.J. (AP) — New Jersey Gov. Chris Christie's former deputy chief of staff testified Friday in her criminal trial that she told him about a traffic study on the George Washington Bridge before sending an email that it was "time for some traffic problems," which prosecutors say started a political revenge plot.

Bridget Kelly is accused of plotting with two other former Christie allies to close lanes on the bridge that connects New Jersey and New York as revenge against a Democratic mayor who wouldn't endorse the Republican governor's re-election effort in 2013.

Kelly maintained Friday that she believed the lane closings to be part of a Port Authority of New York and New Jersey traffic study. She is on trial along with former Port Authority of New York and New Jersey executive Bill Baroni.

David Wildstein, a former Port Authority staffer, previously pleaded guilty in the case and is the prosecution's key witness. The self-described mastermind of the plot, Wildstein has said the traffic study was just a cover story.

Kelly said Friday that Wildstein told her the traffic study would cause "tremendous traffic problems" in Fort Lee, but would ultimately help traffic flow. She said Wildstein suggested holding an event at the bridge with banners saying "Thanks, Governor Christie."

She said Christie said that the study was fine and that she should run it by his then chief of staff. He then asked how their relationship was with Fort Lee Mayor Mark Sokolich, she said.

The release of the "traffic study" email was what blew the scandal into full public view and led to Christie firing Kelly and his campaign manager, Bill Stepien.

"I'm pretty sure if I said it's time for a traffic study in Fort Lee, we wouldn't all know each other," Kelly said.

Wildstein testified earlier in the trial that he did not consider Kelly's email a joke.

Sometimes in tears, Kelly also testified that Christie once threw a water bottle at her, angry that she suggested he introduce local political leaders at an unrelated event. She responded "yes" when her attorney asked her if she was afraid of Christie.

Mike DuHaime, one of Christie's top political advisers, testified that he told Christie ahead of a news conference two months after the lane closures that Kelly and Stepien knew about them.

At the Dec. 13, 2013, news conference, Christie told reporters that no one in his administration other than Wildstein knew about the closings. Asked whether he could say with certainty that no other knew about the plot, Christie said that he had no reason to believe that.

He said he asked everyone on his senior staff to tell him if they had any knowledge "and they've all assured me that they don't." He said that Stepien "assured me the same thing."

Christie was told about the traffic in Fort Lee on the third day of the gridlock during a Sept. 11 memorial event in New York, Wildstein said.

Christie has denied he had any knowledge about the lane closures and hasn't been charged. A spokesman didn't immediately respond Friday to a request for comment.

Stepien's attorney has previously said his client did not engage in wrongdoing of any kind.

While Christie cut Stepien loose in January 2014, he later took a position running a think tank for New Jersey Lt. Gov Kim Guadagno and is now part of Republican presidential candidate Donald Trump's campaign.

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