She met her longtime partner in high school; they moved to the Samuel Gompers Houses on the Lower East Side in the early 2000s with their young son.

With Ms. Fisher increasingly volatile, her partner decided to leave her in 2006, the relative said.

One night before he moved out, Ms. Fisher heated oil in a frying pan on the stove and poured it onto his face, burning and scarring him, according to neighbors and the relative. The man did not press charges, but Ms. Fisher was held for psychiatric observation, the relative said. Yet she gained custody of their son.

In March 2011 — around the same time, she later told jail clinicians, that she was told she had mental illness — she showed up on her former partner’s doorstep with their son, saying she had to leave the boy indefinitely.

“She said she had to get out of town, because people were after her,” the relative recalled.

Alone now in her apartment, Ms. Fisher took to hard living. She drank daily, used marijuana and cocaine and sometimes sold drugs, people in her building said. At times, she menaced her neighbors.

“Every day she was different,” Erwin Castillo, 26, said. “Happy one day, another day mad.”

In September 2011, during a fight with her aunt, Ms. Fisher attacked the woman with a Taser. Then, wielding a steak knife, she stabbed her aunt in her neck, ear and arm, according to a police report.

Sent to jail at Rikers for three months, Ms. Fisher was classified as seriously mentally ill, with paranoid schizophrenia, according to medical records. She told clinicians that a few days before her arrest, she heard voices telling her that her aunt was trying to kill her.

Earlier that year, she told clinicians, she had been hospitalized for a month after voices in her head goaded her to try to kill herself by overdosing on pills. She had stopped taking her medication before her arrest because it was “making her feel funny, feel down,” the records say.