A 48-year-old woman was busted in the stabbing death of an 85-year-old man in his Brooklyn apartment – less than three weeks after she attacked her former boyfriend and was sprung without bail, police and sources said.

Nicole Waiters was hauled in for questioning after police found her and a knife at 501 Lefferts Ave. in East Flatbush just after 10 p.m. Thursday, police said.

Police found Edill Gonzales unconscious with multiple stab wounds across the body inside his apartment. He was pronounced dead at Kings County Hospital, police said.

Waiters was charged Friday with second-degree murder and criminal possession of a weapon.

Investigators are determining the relationship between Gonzales and Waiters –– but police sources said they are looking into whether there was a sexual arrangement between the two in which drugs or money may have been exchanged.

A neighbor in the building told The Post she called 911 after hearing the fatal scuffle through his walls.

“My dresser drawers popped out. He’s screaming. Furniture was falling. He wasn’t screaming no more,” the neighbor said.

“She’s telling me they was in there having sex,” she added.

The neighbor then called police, who took Waiters into custody and rushed Gonzales to the hospital.

In a previous case, Waiters had taken out an order of protection against her former beau, Claing Hendrix, after he choked her, sources said.

The man later showed up at her home on Nelson Avenue in The Bronx about 3:30 a.m. Jan. 6, when she allegedly stabbed him.

Waiters was charged with second-degree assault and released on her own recognizance, despite being bail eligible.

“Waiters is charged with the assault and Hendrix is charged with criminal contempt for violating an order of protection issued in Brooklyn,” said Patrice O’Shaughnessy, spokeswoman for the Bronx district attorney.

“Waiters said Hendrix attacked her and she acted in self-defense. The two have a prior history of (domestic violence) in which he was aggressor. We did not ask for bail as we were continuing to investigate to identify who was the initial aggressor in the Jan. 6 incident,” she added.

A new bail law passed as part of last year’s budget package mandates the release of defendants charged with misdemeanors and nonviolent felonies – but a judge can set bail on a charge of second-degree assault.

Waiters also was slapped with menacing, aggravated harassment and weapons possession charges in connection with the Bronx case.

She has 46 prior arrests, mostly for drug possession and selling, dating back to 1987. She also has been arrested for prostitution, sources said.

Investigators were seen carrying out bags of evidence from the third-floor apartment where Gonzales lived. Police said they found two knives, including one that was covered in blood, drug paraphernalia, condoms and alcohol, according to reports.