Wednesday night, just one day after he filed an appeal, the ex-fiancée of convicted murderer Steven Avery made a stunning reversal from the steadfast, supportive partner she appears to be in Netflix’s hit docuseries Making a Murderer. “Steven’s the one person I don’t trust,” Jodi Stachowski said in an interview with HLN’s Nancy Grace show. “He’s like Dr. Jekyll and Mr. Hyde…behind closed doors, he’s a monster.”

Ten years after the murder of photographer Teresa Halbach and eight years after Avery was sentenced to life without parole for the crime, his former partner made shocking allegations against the Making a Murderer subject to finally reveal “the truth—what a monster he is,” she said. “He’s not innocent.”

Stachowski recalled first hearing that the man she was engaged to was a suspect in Halbach’s 2005 disappearance when she saw the news broadcast in jail. Her gut instinct told her he was guilty “because of the way I know he is.”

“Capable of murder?” led Grace’s interviewer.

“Yeah,” Stachowski replied, nodding. “Hurting people. He told me once, excuse my language, ‘All bitches owe him’ because of the one that sent him to prison the first time. We all owed him.”

Previously, Stachowski claimed to investigators and the Making a Murderer filmmakers that she had two “normal” 15-minute conversations with Avery while she was in jail for a DUI.“I’m looking at the phone bill from October 31,” Stachowski told filmmakers on-camera. “I called Steven at 5:36 p.m.—supposedly when all this murder or whatever was supposedly happening. And we talked for 15 minutes, and the conversation was normal. He didn’t sound rushed or like he was doing anything. And if he was in the middle of doing something, we wouldn’t have talked for 15 minutes.”Now, Stachowski says she lied about the phone calls, and her belief that Avery was guilty, out of fear for her own safety. “He did sound funny. He didn’t sound rushed or whatever, but he did sound funny—like he was lying or hiding something.”A visibly shaken Stachowksi confirmed to Nancy Grace producer Natasha Lance that she believes Avery is guilty of killing Halbach. “Yes I do,” she said, “because he threatened to kill me and my family and a friend of mine.”On one occasion, Stachowski says Avery threatened to burn her house down with her mother and child inside. On another, “I was in a bath and he threatened to throw a blow dryer in there, and he told me that he’d be able to get away with it.”

In the exclusive sit-down interview for avowed anti-Avery crusader Nancy Grace’s program, Stachowski detailed the allegedly abusive two-year relationship she had with Avery—a relationship she now says was marred by his volatile and violent behavior.

“He’d beat me all the time, punch me, throw me against the wall. I tried to leave and he smashed the windshield out of my car so I couldn’t leave him,” she said, saying that she believes the extended Avery family noticed her domestic injuries but ignored them.

Stachowski says she suffered repeated physical assaults at Avery’s hands, including one incident in which he choked her until she lost consciousness only to wake up as he was dragging her to his car. (Calumet County prosecutor Ken Kratz successfully argued in Avery’s 2007 trial that he had transported Halbach’s body in the back of her RAV4.) Stachowski said the police arrived and intervened shortly thereafter. Authorities, however, reported no physical evidence to support Stachowski’s claims.

After authorities zeroed in on Avery as a suspect in the Halbach murder, they combed the Avery property for evidence. While no trace of Halbach inside Avery’s home was ever found, “they did find blood,” Stachowski said. “But it was my blood in the trailer. How they didn’t find any of hers, I don’t know.”

Avery, she also said, was extremely jealous and spied on her when she was with friends, coworkers, and her family. The abuse was so bad, she claims—including Avery slapping, choking, and hitting her, leaving black eyes and fat lips—that she intentionally poisoned herself in an attempt to get outside help.

“I ate two boxes of rat poison just so I could go to the hospital and get away from him, and ask them to get the police to help me,” she said.

Stachowski appears in Laura Ricciardi and Moira Demos’s 10-part docuseries in taped interviews and observational footage that frame her as a steadfast supporter of Avery and his innocence—until police harassment by local authorities, trying to turn her against Avery, proves too much to bear.The film suggests that Stachowski broke up with Avery and moved away from Manitowoc County, Wisconsin, because of the intense police scrutiny, not because of Avery’s alleged abusiveness. In the interview for Nancy Grace, Stachowski now says she asked the directors to leave her out of the film and that the hit documentary is “all lies.”

“It was all an act,” said Stachowski, who hasn’t seen Making a Murderer. She now claims that she pretended to be supportive of Avery because she was afraid he would hurt her otherwise. “He told me how to act. He said smile, be happy. I didn’t know what to do. I didn’t want to get hurt.”

Stachowski said she hasn’t seen Avery since leaving Manitowoc, but has received blackmail demands from him as recently as September, threatening to tell police she’s been drinking and driving and driving without a license.

The surprise revelation marked a coup for Grace, who’s taken it upon herself to wage an intense media crusade against Avery. Earlier this week, she even faced off against New Kids on the Block member Donnie Wahlberg over the controversial case.

In the Nancy Grace interview, Stachowski broke down in tears theorizing that if she had been released from jail the day of Halbach’s disappearance as planned, Avery would have picked her up to attend an alcoholism program—and, she believes, Halbach would not have died: “She’d still be alive, because I would have been there.”Stachowski admitted that she doesn’t remember if she ever spoke with Avery’s defense attorneys Dean Strang and Jerry Buting back in 2007. At one point, however, she was set to testify as a witness in the Halbach murder trial—against Avery.On Wednesday, Stachowski says she never went to the authorities with the truth because she was afraid he’d be released and come after her. She also revealed that she never loved Avery.Stachowski believes Avery’s nephew Brendan Dassey, who was 16 years old when he confessed to helping Avery rape and murder Halbach, is not guilty. “I believe he’s innocent,” she said. “I believe Steven threatened Brendan…if Brendan didn’t do what Steven said, he’d hurt him.”“Hurt him how?”“He’d probably end up killing him, too.”