Eleanor Riley, who has two daughters with her former husband, appeared at the Southwark Crown Court overnight as a witness in the trial in which Cairns faces charges of perjury and perverting the course of justice.
The couple divorced in 2012 and she has since remarried. Asked whether they had parted on good terms, she said: "No, not at all."
Under questioning by Crown prosecutor Sasha Wass QC, Mrs Riley told the jury about an evening of eating and drinking in Hale in 2008.
Her husband was playing cricket for Lancashire, while Cairns was playing for Nottingham.
The Vincents had dinner with Chris and Mel Cairns, who was then his girlfriend, and Stu Law - the captain of Lancashire - and his wife at a Thai restaurant.
The Laws then left, while the Vincents and Cairns caught a taxi to the Manhattan Bar and Grill to keep drinking. There they met Andrew Flintoff, the star English allrounder, but Mrs Riley said he had no part in the conversation which she said followed.
Lou Vincent had earlier confessed to his wife of matchfixing and told her that Chris Cairns organised it.
At the bar, Mrs Riley said she spoke to Cairns because she was concerned they would get caught matchfixing as too many players were involved and Vincent had a "tendency to talk to anyone who listened".
She said Cairns assured her that "everyone was doing it in India" and they weren't going to get caught. "He was very confident about that."
Mrs Riley said Mel Cairns - whom she just met that day - joined the conversation and also assured her.
Chris Cairns' defence lawyer, Orlando Pownall QC, suggested Mrs Riley was wrong about the conversation about matchfixing, apparently with someone she had just met, and she was "infected" by the intoxicating effect of alcohol.
She replied to say she had eaten a five course meal at the Thai restaurant. "When I've had a large meal it doesn't matter how much I drink, I'm as clear as a bell."
It was revealed in court that Mrs Riley had been told that morning that she would not be charged by police for her knowledge of money her husband had received for match-fixing. But this was not part of an immunity deal for her to give evidence in the trial.
Mrs Riley said she was not worried about being prosecuted until it was raised as a possibility by lawyers she met a few months ago.
She said a previous statement to ICC investigators, in which she mentioned being worried about being "dragged down with this", was in regards to her acrimonious split with Vincent.
He had threatened to use her knowledge of his crimes against her, which made her scared of losing custody of their children.
"When I was with Lou, he was very scared that I would use matchfixing against him. He said he would use [her knowledge] against me, take me down with him."
She told the jury that Vincent told her he would give evidence against Cairns in order to escape charges. "He told me that in exchange for letting the ICC know the big name, and all the other names, then he would come clean as long as they wrote a letter to stop him from going to jail."
Vincent last week told the court that he was not offered immunity from prosecution and was given a formal caution from the trial judge that he did not have to answer questions which might incriminate himself. He later admitted committed crimes in the United Kingdom.
Mrs Riley told the jury that Vincent had a second phone and an "underground email" solely used to communicate with match-fixers. She spoke of how her husband rang her in tears once, confessing for the first time to match-fixing, as he had "stuffed up" a game for Cairns by hitting a six.
She also agreed with Mr Pownall that Lou Vincent "hated Chris Cairns" and later clarified that was because Vincent claimed to be owed $US250,000.
One day, when Lou Vincent was playing for Lancashire, he was in the park enjoying some family time when his phone rang. He had promised to not fix any games in the United Kingdom, said Mrs Riley, and acted "shifty" during the phone conversation.
She assumed it was Cairns calling, but did not hear his voice. Vincent later told her that it was Cairns who asked him to fix a game for Lancashire, but he refused.
Mr Pownall showed her some Facebook messages exchanged between Mrs Riley and Mel Cairns, one dated a few days after Chris Cairns was suspended from the Indian Cricket League in October 2008. Mrs Riley wrote it was "was a huge shock when Lou told me".
Asked to explain what Vincent had told her, Mrs Riley said Cairns had been suspended for match-fixing but the official reason given publicly was an undisclosed leg injury.
Answering some final questions from the Crown prosecutor, Mrs Riley was asked whether she had any reason to lie about the conversation where Cairns allegedly reassured her they would not be caught match-fixing.
"No, not at all. I certainly wouldn't come to a perjury trial to lie."
And did she have any reason to support her ex-husband? "None at all."
- Jared Savage in London
