Cops charged a 15-year-old Brooklyn girl with murder Monday after she confessed to killing her mom and the woman’s boyfriend, sources said.

Destiny Garcia claimed she blew away her mother, Rosie Sanchez, 38, and Sanchez’s beau, Anderson Nuñez, 40, because Rosie abused her and Nuñez did nothing to stop the violence, according to authorities and other sources.

But “we don’t think at all this was an act of self-defense,’’ said NYPD Chief of Detectives Robert Boyce. “What she said was basically the mother was physically abusive to her in the past . . . She went and got a gun.”

In the days leading up to the Dec. 26 shooting, the teen called a 15-year-old male friend upstate and convinced him she was being raped by Nuñez, she told police.

Investigators believe she was lying, but the claim was enough to prompt the boy to leave his boarding school and make the trip to the Big Apple — bringing with him a gun that Destiny stashed in a drawer, the sources said.

The pair met up at Destiny’s Brooklyn house, sources added.

After confronting her mother later that day and allegedly pumping a bullet into her ear, Destiny set her sights on Nuñez — shooting him once as he tried to stop her, sources said. But he was only wounded and continued toward her, the sources said.

“I need help! I need help!” Destiny allegedly screamed to her friend as she fought off Nuñez.

Her pal grabbed the gun and fired — striking the boyfriend once in the back, according to cops. Destiny then finished the job by stabbing him “over 30 times” said prosecutor Tziyonah Langsam at Destiny’s arraignment in Brooklyn Criminal Court on Monday night. She also allegedly stabbed her mom.

A source said, “She stabbed [Nuñez] after he was already shot,” and alleged that Destiny plunged a knife into Nuñez’s neck and torso.

The teens then fled.

Rosie Sanchez’s mother called the cops after not hearing from her daughter for a few days. Police went to the home and discovered the bodies Sunday night.

Destiny was tracked down at the Brooklyn home of her father, Roldolfo Richardson, and taken into custody. Her friend is still at large.

She was held on two counts of second-degree murder and weapons possession as an adult. Her next court date is Jan. 6.

Neighbor Tiffany Jackson, 21, said she could sense tension between the mom and daughter.

“It looked like they had problems,” she said, referring to their body language when together.

Additional reporting by Sarah Trefethen