The girlfriend of a slain drug dealer, who had balked at testifying against his accused slavers Monday, returned to the witness stand yesterday after obtaining a 24-hour furlough from prison to visit her young son.

"This woman is extorting a furlough from the government from her testimony . . .The government has purchased her testimony . . . and it's outrageous," said defense attorney Stephen O'Brien who along with the second defense attorney, George Mitchell, opposed the resumption of testimony after a three-day delay.

Jennifer Pinkett, 27, told D.C. Superior Court Judge John F. Doyle that she was afraid to continue her testimony against two brothers, Nathaniel and James McQueen, who are on trial for the murder of Ralph Payne, 37, in his 16th Street NW apartment a year ago.

Pinkett is serving a two-year sentence for narcotics possession at the Alderson prison for women in West Virginia and was returned to the District to testify in the murder trial.

Under questioning yesterday by Assistant U.S. Attorney James Hanney, who helped negotiate the furlough, she said she was still frightened but requested the furlough in return for testifying because:

"My little boy is seeing a psychologist every day. The main reason is because I'm incarcerated . . . He has told the psychologist he would do something bad to himself because he knows then I can come home."

She said that neither McQueen had threatened her.

Most of the cross-examination of Pinkett by O'Brien and Mitchell was aimed at discrediting her as a witness. She is the only eyewitness to the noon-time shooting, authorities have said.

Under questioning yesterday she admitted that she was a heroin user and had taken some two days before the murder. She also said that she lied to police detectives who first talked to her after the murder when she denied her drug use, and said that she had taken heroin the night after the murder because "I wanted to get high and to see if there was any talk uptown (on 14th Street NW) about it (the murder)."

Homicide Detective Robert Chaney, the principal investigator of the murder, testified Tuesday that he asked Pinkett to go to 14th Street to see if she could learn anything about the shooting that would assist police.

She also said that she had lied when she wrote a friend that she had smoked marijuana while in jail, but she admitted trying unsuccessfully to get drugs smuggled to her in jail.