Lauren Alleyne, 21, was originally charged with murder in the killing of Io Nachtwey, 22, on Nov. 3, 2001.

She pleaded guilty to manslaughter and kidnapping today in a plea deal. She has agreed to testify against the remaining four defendants in the case as part of the deal, said her attorney, Stephen Hrones.

Alleyne is expected to receive a sentence of 12 to 15 years in prison, Hrones said.

Last month, Ana White, 21, pleaded guilty to the same charges and agreed to testify against the others. She is expected to receive a sentence of 12 years.

Nachtwey was one of the homeless people who regularly begged for handouts at "The Pit," a sunken brick plaza above the Harvard Square subway station.

She had landed in Boston during the summer of 2001 after dropping out of Maui Community College and traveling to the East Coast to stay with grandparents in Maine, friends said.

She would panhandle outside shops at the square, always with a smile. Just a few years before, Nachtwey had been named the best female dancer in her senior year at King Kekaulike High School on Maui, and friends said she would often give an impromptu dance in the square.

At night, when many of the other kids go home, Nachtwey would curl up to sleep with other homeless in a Harvard Square cemetery.

Prosecutors said two brothers, Luis and Ismael Vasquez, and two other defendants, Harold Parker and Scott Davenport, were recruiting homeless people into a robbery ring. On Halloween night 2001, the new recruits, who were Nachtwey's friends, were ordered to steal valuables as a gang initiation.

But when Nachtwey's friends failed to bring back any goods three days later, Nachtwey was killed to send a message to her friends, prosecutors said.