A Brooklyn throat-slashing victim allegedly killed by an estranged boyfriend had been badly battered by him in the past and forced to flee to domestic violence shelters as recently as January, the victim’s sister told The Post.

Eryka Caldwell, 41, was trying to kick 38-year-old Jonathan Fernandez out of the Bushwick apartment Sunday morning when prosecutors said the accused killer allegedly went into a rage and slit the victim’s throat — then sat calmly on the sofa and waited for cops, authorities said.

“She tried to find the good in everybody,” Caldwell’s sister, Contessa, said during a telephone interview.

“If there was just a monster or evil, she still tried to find the smallest good in that person,” the grieving sibling said. “And this time, [there] just was no good for her to find or her to fix.”

Caldwell, who moved from Kentucky to the Big Apple at age 18, had only moved into the Bushwick apartment in March but had been unable to keep the ex-lover away, Contessa said.

Fernandez already had a string of busts for robbery, burglary and theft of service dating to 2015 — including an alleged assault of Caldwell in 2024, according to law enforcement sources.

As many as 20 other arrests have since been sealed.

“He was arrested in January, and then it was two more incidents,” Caldwell’s sister said. “I don’t know if he was arrested for them, but I know it was two more incidents where police had to come to the scene and it was domestic violence.

“He did not get locked up,” she said. “They moved her to two different shelters. After he got arrested, he still found her, I don’t know how that went.”

She said her sibling — who identified as a “proud trans woman” — even kept the troubled relationship a secret from the rest of the family.

“When it came to her relationships, if it was abusive or anything, she didn’t allow me to know,” she said.

“I just wish she would have reached out for help or told somebody in code or something,” she added. “Like, what was going on, so she could have gotten the help or somebody could have come down there.”

Around 8:50 a.m. Sunday, Caldwell texted 911 for help, and cops arriving at the scene frantically tried to get through the door as screams could be heard coming from inside.

“Help me, he’s stabbing me,” the victim yelled out to the officers, according to prosecutors.

Police eventually were able to climb in through a window by pushing in an AC unit — and allegedly found Fernandez sitting calmly on the couch while the bloodied victim lay dying at his feet in the blood-soaked room, prosecutors said.

The accused killer, who is facing second-degree murder and other charges, appeared in court for the first time on Monday night wearing a white Tyvek suit. His attorney requested a psych evaluation and he was ordered held without bail at Rikers Island.

According to Brooklyn prosecutors, Fernandez bizarrely claimed self-defense.

“The victim started swinging a knife, so the defendant swung the knife too and hit the victim first,” Assistant District Attorney Tziyonah Langsam said, describing the accused killer’s claims.

Fernandez is due back in court for arraignment on Friday.