She was Bonnie to his Clyde, federal authorities say.

And for most of the last decade, investigators allege, they were partners in a criminal enterprise that trafficked in cocaine and prostitution, and bribed witnesses to keep them from talking - and when that wasn't an option, resorted to murder to shut them up.

Originally charged as a minor player, Yolanda Jauregui, 37, has been portrayed in recent court filings as a key figure in the operation headed by her boyfriend, Paul Bergrin, a rogue Newark, N.J., defense attorney.

Now held without bail, Jauregui (pronounced HOW-reh-gee) was arraigned on a drug-trafficking charge on Monday, the latest twist in a case that reads like the script of a Quentin Tarantino movie.

Authorities allege that while free on bail during the summer, she sold a kilogram of cocaine to a federal informant and an undercover FBI agent for $35,000.

"You know how we make money," she allegedly told the informant while cautiously negotiating the deal.

The timing of the transaction - Jauregui is accused of setting up the deal just a week after she was released on bail - underscores what investigators have described as the audacity of the petite, dark-haired woman.

But from a criminal perspective, the kilo sale is the least of her problems.

When the Bergrin racketeering case broke on May 20, Jauregui was charged with just two counts of wire fraud, but her boyfriend and two other defendants were charged with murder, murder conspiracy, bribery, and other counts. A superseding indictment unsealed last month expanded the charges against her to include racketeering, drug trafficking, and conspiracy to commit murder. As a result, Jauregui faces a potential life sentence.

Authorities now say she was one of the first to suspect - accurately, it turned out - that a Chicago hit man brought in to rub out a witness was a government informant and that she threatened to have him killed if her suspicion proved true.

According to the indictment, Jauregui attended several meetings with Bergrin and the hit man, and expressed concern that the would-be shooter "was taking too long to locate and kill" a witness against a reputed Monmouth County drug kingpin Bergrin was representing.

Jauregui said "she had done a background check on the hit man and . . . was worried . . . [he] may have been a law enforcement cooperator," the indictment alleges. She threatened to have the hit man "boxed and sent home" if that proved true.

The hit man, who has not been identified by name, recorded dozens of conversations for the FBI.

The sprawling racketeering case is built around thousands of wiretapped conversations and testimony and secret tapes made by several cooperating witnesses.

Bergrin, who authorities say provided "legal and illegal services to various criminals," has been the target of a federal probe for the last six years.

He is a former Essex County assistant prosecutor and assistant U.S. attorney whose criminal clients have included several major North Jersey drug kingpins. It was the murder of a witness scheduled to testify against one of his clients in November 2003 that first attracted the attention of federal authorities, sources familiar with the probe said.

The association between Jauregui, also known as Yolanda Bracero, and Bergrin, 53, dates back about nine years, according to those familiar with the case.

Their relationship was economic (they set up several businesses together). It was romantic (they lived together in Nutley at the time of their arrests). And, a 39-count indictment alleges, it was criminal.

Bergrin, who is married, opened a restaurant with Jauregui and set up two other businesses, including a real estate company that authorities allege engaged in mortgage and wire fraud.

Investigators say the now-shuttered restaurant, Isabela's on Summer Street in Newark, was a stash house for large quantities of cocaine. More than 100 pounds were found there after Bergrin and Jauregui were arrested in May.

Authorities also allege that after Bergrin was arrested in 2007 for his involvement in a $1,000-an-hour call girl operation in New York City, Jauregui plotted to have a witness against him killed and agreed to pay $10,000 for the murder contract.

Neither the drug dealing nor the murder conspiracy charges were part of the case against her when she was first arrested.

Authorities allege that while Jauregui was free on bail in the spring, she returned to the drug underworld because she needed cash. She had several meetings with a potential customer but moved cautiously, according to a criminal complaint filed by an FBI agent involved in the case.

At one meeting, she had the man, who was seeking to buy cocaine from her, strip-searched in the bathroom of a North Jersey diner to ensure he wasn't wearing a wire, the complaint alleges. She also made him remove the battery from his cell phone during their meeting.

As with the hit man from Chicago, her suspicions were well-founded. The customer was cooperating with the FBI.

During several meetings with the informant between May 27 and June 22, Jauregui talked about her need to get money, expressed concern that she was being watched by law enforcement, alluded to her drug connections, and cautioned her would-be customer to be careful "because you never know who is behind you," according to the criminal complaint.

Authorities say Jauregui set up the drug deal for June 16 at a restaurant in Nutley, but panicked and backed away when the informant showed up with a woman she did not know.

The informant identified the woman as his cousin. She was actually an FBI undercover agent.

"I got freaked out because of the girl," Jauregui told the informant days later while agreeing to set up another exchange, the complaint alleges.

On June 22, Jauregui met the informant and the undercover agent at a shopping center in Clifton. There, authorities charge, "Jauregui obtained . . . $35,000" from the informant. She then "had an associate deliver a shopping bag containing a kilogram of cocaine" to the undercover FBI agent.

Jauregui pleaded not guilty to a cocaine-distribution charge during Monday's brief arraignment before U.S. District Judge William J. Martini. A trial date has been set for February.

Bergrin, Jauregui, and six other defendants are scheduled to be tried on the racketeering charges in June.

Contact staff writer George Anastasia at 856-779-3846 or ganastasia@phillynews.com.