"My life is shattered in pieces," Sabourin said.
Sabourin, 41, a Canadian publicist and actress, met Baldwin in 2000 during the filming of the sci-fi comedy The Adventures of Pluto Nash. He had a cameo, and she was a publicist.
The two had dinner together in New York in 2010, both sides say.
Baldwin and prosecutors say she then conducted a campaign of harassment that escalated from phone calls and emails to showing up uninvited at his homes.
"It was nightmarish," Baldwin, 55, testified. He likened the situation to an Alfred Hitchcock production.
Baldwin "became very flirtatious" at their first meeting in 2000 and invited her to visit him at his Hamptons home, Sabourin said as her testimony began. She says the two had a sexual and romantic relationship, which Baldwin denied on the witness stand.
Meanwhile, another Hollywood figure became an issue in the case: Scarface and Dog Day Afternoon producer Martin Bregman, who was also a producer of Pluto Nash.
Baldwin testified that Sabourin was Bregman's mistress and that Bregman asked the actor to give her advice. The married Bregman, however, later said by phone that he "never had an affair with her" and was shocked that Baldwin had said otherwise.
Sabourin also says she and Bregman weren't romantically involved.
Bregman said he thought Baldwin had found Sabourin attractive, but "I don't know if anything happened between the two of them".
Prosecutors included Bregman on their list of potential witnesses but didn't call him because he told them "he had little to say about this incident," Manhattan Assistant District Attorney Zachary Stendig said.
But Mandelbaum agreed to what's called a "missing witness" instruction, allowing him to infer that Bregman's testimony wouldn't have been favourable to the prosecution.
Bregman isn't expected to testify for the defence, either.
- AP