BOSTON (AP) The longtime girlfriend of reputed mobster James "Whitey" Bulger will plead guilty to helping him evade capture but won't testify against him at his trial, prosecutors and relatives of people he's accused of killing said Monday.

Catherine Greig, 60, was charged with conspiracy to harbor a fugitive after she was captured with Bulger in Santa Monica, Calif., in June, more than 16 years after Bulger fled Boston.

Late Monday, prosecutors, after meeting with about a dozen people who say their relatives were killed by Bulger, filed a superseding indictment against Greig, adding charges of identity fraud and conspiracy to commit identity fraud.

Under a plea agreement, also filed late Monday, Greig will plead guilty to all three charges Wednesday.

Each of the charges carries a maximum penalty of five years in prison, but prosecutors told the families that Greig could face as little as 32 months in prison under federal sentencing guidelines.

In the plea deal, prosecutors said they have agreed not to charge Greig with any additional offenses. They said they will not make a sentencing recommendation and reserve the right to seek a sentence higher than a range to be calculated under federal guidelines.

Bulger, 82, headed the notorious Winter Hill Gang and was a top-echelon FBI informant who ratted out the rival New England Mafia. His former FBI handler, John Connolly Jr., was convicted for warning him that he was about to be indicted, prompting him to flee Boston in late 1994.

Bulger is charged with participating in 19 murders. He has pleaded not guilty.

In a statement of facts signed by Greig and filed in court Monday, Greig acknowledges that she agreed to join Bulger on the run beginning in early 1995.

She also admits she agreed to conceal him from authorities for 16 years, used aliases, possessed unlawfully obtained identification documents such as driver's licenses and Social Security cards of other people and repeatedly helped him obtain prescription medication from a pharmacy by claiming to be his wife.

"I engaged in conduct that was intended to help Bulger avoid detection from law enforcement and to provide him with support and assistance during his flight from law enforcement," the document states.

"Together, we falsely posed as a married couple. ...I also told false cover stories to people we met in Santa Monica in order to conceal our true identities from law enforcement," the document states.

Tom Donahue, who says his father, Michael Donahue, was killed by Bulger and another man in 1982, said he was angry about what he called a "sweetheart deal" and a "slap on the wrist" for Greig.

"I'm not happy with the deal," Donahue said. "She helped keep that guy on the run. We could have had questions answered 16 years ago."

Michael Donahue's widow, Patricia Donahue, said prosecutors told the families they could not force Greig to testify against Bulger.

"They said, 'We cannot make anybody do anything they don't want to do,'" she said.

Patricia Donahue and her son said prosecutors told the families they did not want to risk Greig getting acquitted at trial.

Steven Davis, who says his sister, Debra Davis, was killed by Bulger, said he had mixed feelings about Greig avoiding trial.

"I mean, she's going to get what's coming to her ... it's never going to be enough," he said. "You can't bring my sister back."

Davis said the families met for a little over an hour with U.S. Attorney Carmen Ortiz and assistant U.S. attorneys.