As early as May 2003, France's famed antiterrorist investigating judge, Jean-Louis Bruguière, warned that European terrorist networks were trying to recruit Caucasian women to handle terrorist logistics because they would be less likely to raise suspicion.

He said then that it was only a matter of time before the women moved on to more violent acts.

Ms. Degauque was born in the small suburb of Charleroi, a gritty coal and steel town where her father operated a crane at the sprawling smelter, according to neighbors and friends.

She grew up doted on by her mother, Liliane, who worked as a cleaner and monitor at the local elementary school.

"Her mother spoiled her," said Jeannine Beghin, who has known Ms. Degauque's mother since childhood. Ms. Beghin recalled that Ms. Degauque's mother rented out a hall and gave a catered party with music and dancing to celebrate the daughter's first communion.

"Muriel had the prettiest dress of all the girls," Ms. Beghin said.

Her teachers remember her as a well-dressed, well-behaved young woman, even if she was a middling student. "Muriel was more literary than scientific," said Rita Detraux, a retired high school teacher. Still, Ms. Degauque seemed adrift by the time she took an apprenticeship as a sales clerk at a bakery in Charleroi after her third year of high school. The local press has quoted her former boss as saying that Ms. Degauque would disappear at lunchtime, and that he soon learned she was using drugs.

Talk that Ms. Degauque had fallen into the wrong crowd soon circulated in the neighborhood. The Belgian Police say she became known as a drug user, though she was never arrested. In her late teens, she followed her older brother in joining a local motorcycle club, the Apaches, and neighbors saw her come and go in a black leather jacket on the back of a boyfriend's motorcycle.

By most accounts, Ms. Degauque's wayward streak took a decisive turn when her brother was killed in a motorcycle accident when she was 20. He had always been the more popular of the two, people who know the family say. One neighbor, Andrea Dorange, has told local newspapers that Ms. Degauque said she should have died instead of her brother.