The busty brunette wore white combat pants tucked into knee-high red boots to her arraignment on murder, racketeering and assault charges in Manhattan federal court.

Her fingernails were painted black.

And according to federal authorities, Maria Mejia, 24, was a femme fatale, the leader of a Bronx girl gang called the Bad Barbies, who specialized in what one gang expert called “the Venus fly trap” — coaxing rival gang-bangers into various traps where they would be brutally gunned down or hacked with machetes.

In 2011, Mejia was accused of “luring a robbery victim to the front of a Mexican bar where he was shot” by members of the Trinitarios, the same gang accused of dragging Bronx teen Lesandro Guzman-Feliz out of a neighborhood bodega and savagely stabbing and hacking him to death last month.

Several years earlier in 2005, federal authorities say Mejia tricked a 20-year-old from rival gang Dominicans Don’t Play into a trap that resulted in his murder.

Mejia was caught in a gang sweep with 39 members of the Trinitarios in 2012, which included nine charges of murder and 24 of attempted murder against the gang members in addition to several charges of assault and racketeering. Her involvement in a notorious macho Latin gang — the only woman to be charged — made seasoned law enforcement officials sit up and take notice.

“We were not surprised that the Trinitarios were up to no good in the Bronx — but the Bad Barbies? Who knew?” former NYPD Commissioner Ray Kelly said at the time the indictments were handed down. “Apparently, it is a sign that gender is no bar when it comes to crimes of robbery and murder and other serious offenses.”

Mejia and her millennial molls were suddenly on the rise, acting as groupies to one of the city’s most savage street gangs — an organization the FBI called “the most rapidly expanding Caribbean gang and the largest Dominican gang” in America. But the Bad Barbies — tough-talking teens and twenty-somethings famed for their tight jeans and long painted fingernails — are just as lethal as their criminal cohorts.

There are more than 100 women associated with the Trinitarios at any one time, Kelly said in 2012.

In most cases, even the most notorious members of the Bad Barbies — also known as One Seven Hoes — are considered the property of male Trinitarios, and are regularly raped or pimped out among the crew, according to the 2012 federal criminal indictment.

In addition to their role as sex slaves, the Bad Barbies have also been known to act as decoys and mules, often carrying weapons and hiding drugs for their male overlords, said Curtis Sliwa, founder of the Guardian Angels and a gang expert.

“Female Trinitarios’ members have been known to hide sawed-off machetes and drugs such as heroin, fentanyl and marijuana in baby strollers when police arrive on the scene,” said Sliwa.

“The male members know that it’s rare that police will ever search women, especially ones pushing a baby carriage,” he said, adding that gang members rounded up in New Jersey, Washington Heights and the Bronx are rarely caught with weapons.

Sliwa said he witnessed the steady rise of the Trinitarios in Washington Heights, where the Guardian Angels patrol, throughout the 1990s. The gang was founded on Rikers Island in the late 1980s by convicted murderer Leonides Sierra to protect himself and fellow Dominican inmates from attacks by rival gangs, including the Bloods and Latin Kings. Sierra is still in prison and has been accused of leading gang activity from his cell in Attica.

Although the gang’s early leaders took inspiration from a trio or “trinity” of 19th-century Dominican freedom fighters, their ideals of liberty and equality clearly do not stretch to their female members.

The Bad Barbies are always expected to be on call for their male leaders, law enforcement sources told The Post.

The women help Trinitarios gang members with providing safe houses to store drugs and hide from law enforcement. Often male gang members will hole up in homes in New Jersey and the Bronx that are maintained by female members, Sliwa told The Post.

“They often have all the news clippings about them taped to the walls of these safe houses because they love publicity,” he said. “And the most recent publicity from the murder of Guzman-Feliz just makes them all the more notorious and feared.”

The Trinitarios’ misogyny and patriarchal rule of the women in their circle is in direct contrast to other Latin gangs, including their rivals the Latin Kings. Founded in Chicago in the 1940s by Mexican immigrants and Puerto Ricans, this highly organized criminal enterprise puts male and female members on an equal footing, gang experts say. If a woman has a higher rank within the gang hierarchy, male gang members are required to take orders from her. Women are so important to the organization that they have their own faction known as the Latin Queens.

While authorities described Mejia as the leader of the Bad Barbies, she was still under the thumb of her male overlords, Sliwa said. Most women in the Trinitarios’ orbit are still used to “diss and dismiss” enemy gangs.

“It used to be that rival gangs threw up graffiti to diss each other,” said Sliwa. “Now they rape each other’s girlfriends or female gang members and upload the sex tapes to social media sites to embarrass their rivals.”

Cops say a sex tape led to the brutal murder of Guzman-Feliz.

In a seconds-long video viewed by The Post, a teen girl lies nude on a bed and covers her face with a white towel. She is repeatedly penetrated by a man wearing shorts, while a male teen raps in the foreground, seemingly oblivious to the sordid scene taking place behind him. Much confusion remains about the origins of the video. It is still unknown who shot it and how it ended up on the internet in the first place. What is known is that the video angered the gang or someone close to the gang, police say.

And while the rapper in the tape bears a strong resemblance to the murdered teen, it was not Guzman-Feliz. The Trinitarios gang members who killed Guzman-Feliz on June 20 with machete blows to the neck and stomach in a savage revenge attack recognized their mistake only after the teen, who was known as Junior, was already dead.

Police charged eight suspects linked to the slaying in New York and New Jersey last week with murder, manslaughter, gang assault and the criminal possession of a weapon. Six of the suspects picked up in Paterson, NJ, were extradited to the Bronx. All pleaded not guilty. They are due back in Bronx criminal court tomorrow.

After Trinitarios members apologized for targeting the wrong teen, some social media users directed their anger at the teenage girl in the video, although there is no consensus about who she is. Her face appears only fleetingly, and most of the time she hides behind the white towel. Police say they are providing protection for a teen after she received hundreds of online threats, many of them blaming her for the death of Guzman-Feliz.

Whoever the girl is, her treatment is emblematic of the way the gang views the opposite sex.

Mejia knew what the Trinitarios were capable of, which may have been why she denied having anything to do with them in court. Through her lawyer, she said she was “a homemaker” who cared for her ailing mother and had nothing to do with street gangs.

Little is known about her case, much of which is under federal seal. Though reporters were able to describe her appearance in court, the media was never able to take or find pictures of her — not even a mug shot.

Although a federal prisoner database indicates that Mejia, now 30, was registered to a federal prison, her whereabouts are unknown and there is no scheduled date for her release.