The 48-year-old woman charged with fatally stabbing an 85-year-old man in his Brooklyn apartment was held without bail —after prosecutors revealed she had an “on and off” relationship with the victim for 14 years.

Nicole Waiters was arrested after investigators found her — and a knife — at victim Edill Gonzalez’s apartment on Lefferts Ave. in East Flatbush, officials said.

Police had discovered Gonzalez Friday with multiple stab wounds “lying in a bed with blood soaked bedsheets gasping for air,” a criminal complaint says. He was later pronounced dead at Kings County Hospital.

Waiters appeared in court Saturday on charges of second-degree murder and criminal possession of a weapon. Assistant District Attorney Christopher Myco told the judge she and Gonzalez were “on and off for 14 years”—despite a 37-year age difference.

The nature of the pair’s relationship was not immediately clear, though investigators are looking into whether there was a sexual arrangement between the two in which drugs or money may have been exchanged, police sources told The Post.

Waiters claimed she had acted in self-defense during the deadly stabbing, stating that Gonzalez “grabbed three knives and rushed at [her],” forcing her to attack him, court records show.

But an elderly neighbor in the building who called 911 after hearing the scuffle told The Post that when he complained about the noise of the scuffle in their apartment, Waiters told him that the pair were “in there having sex.”

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

Waiters had previously been busted for attacking former beau Claing Hendrix after he showed up at her Bronx home Jan. 6, violating an order of protection she’d received after he allegedly choked her.

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

“We did not ask for bail as we were continuing to investigate to identify who was the initial aggressor in the Jan. 6 incident,” said Patrice O’Shaughnessy, spokeswoman for the Bronx district attorney.

At Saturday’s proceeding, prosecutors requested that Waiters—who has 46 prior arrests dating back to 1987—be held without bail, which Judge John Hecht granted.

She is expected to return to court Jan. 30th.