France’s most-wanted woman once loved the warm waves of the Dominican Republic, posing in a black bikini with her future husband, a petty thief. As her faith deepened, she exchanged the bathing suits for head scarves and new destinations: mosques in Malaysia, a pilgrimage to Mecca and now, authorities say, the jihadist cauldron of Syria.

Hayat Boumeddiene said she lived to travel, and now she is on the lam. She fled into the arms of the Islamic State the day before her husband attacked a kosher grocery in Paris on Jan. 9, investigators say. The militant group’s self-proclaimed caliphate spanning Syria and Iraq is drawing aspiring fighters from around the world, including a growing number of women.

With her husband dead, along with the two other men who carried out the Paris attacks last month, Boumeddiene, a 26-year-old native of France, is emerging as a key target for investigators, who think she knows crucial details about the planning of the three days of violence that terrorized France and claimed 17 victims. Understanding Boumeddiene’s path to radicalization is especially valuable, authorities say, since they believe that women are increasingly the backbone of such plots. A copy of a jihadist text written by a prominent Belgian woman with ties to al-Qaeda, Malika El Aroud, was found among Boumeddiene’s possessions after her disappearance.

Much remains unclear about Boumeddiene’s role in the Paris attacks. But she fled France days before the violence, and authorities believe she played a key role passing messages as the plot took shape. Records show more than 500 calls in 2014 between her phone and that of the wife of Chérif Kouachi, one of the two brothers who attacked the offices of the satirical newsweekly Charlie Hebdo on Jan. 7.

Interviews with friends and family as well as investigation files show a long road to disillusionment with the West for Boumeddiene. The journey began in Paris’s tense suburbs and culminated with the bloodshed that has Europe fearing more attacks.

Now counterterrorism authorities are asking themselves whether they should have paid closer attention to Boumeddiene, who once wore a full-face veil as she practiced firing a crossbow with a man considered one of al-Qaeda’s top recruiters in Europe. Authorities never previously believed she was a danger, though they now say she may have been the force behind her husband, a dissolute 32-year-old French citizen with a long string of robbery and drug-dealing convictions.

“Boumeddiene is now on the wanted list of all European services,” said a European intelligence official. “She is one of the people who can shed light into the network.”

A difficult past

Boumeddiene’s troubles started when she was 8, when her mother died suddenly from a heart ailment, family friends say. Her father quickly remarried. The new wife clashed with her six stepchildren, including dreamy-eyed Hayat, in cramped quarters in a public housing complex in Villiers-sur-Marne, a hard-luck suburb of Paris.

Boumeddiene was placed in a group home at 13, with a family that came from the same Algerian city as her father. She broke from her family, with whom she remained only sporadically in touch.

“This girl didn’t grow up in my house. She grew up in the house of nonbelievers,” said Boumeddiene’s father, Mohamed Boumeddiene, reached by phone in Algeria, where he traveled after the attacks. “She made all these decisions on her own.”

Hayat Boumeddiene favored makeup from Sephora and rambling phone calls with her friends, said Omar, her foster brother, who spoke on the condition that his family’s last name not be published. “She was fragile,” he said, and clearly shaken by her mother’s death. But he said she was also studious and hard-working, holding down a part-time job at a newsstand in a Paris train station even as she attended high school classes.

When she was 18, she rejected a suitor, whom her foster family had found for her in Algeria, and moved on her own to Paris. Within a year, a mutual acquaintance introduced her to Amedy Coulibaly. The French native, whose parents emigrated from Mali, was fresh out of prison for armed robbery. In prison, he had met at least one of the men who would attack Charlie Hebdo.

Neither of the couple was especially religious, Boumeddiene would later tell investigators, but they explored their deepening Islamic faith together. In 2009, two years after they met, they married in a religious ceremony, although such marriages are not recognized by French law.

“I had a difficult past, and this religion answered all my questions and brought me peace,” Boumeddiene told police in 2010, according to a transcript of an interrogation after Coulibaly was charged with trying to break a top militant out of a French jail.

She said she quickly became more observant than her husband. He prayed at the mosque “on his own timetable,” every three weeks or so, she said. Boumeddiene, meanwhile, started wearing a full-face veil and quit her job as a cashier at a bakery. She drew “aggressive looks” from her fellow countrymen on the street, she said, adding that it was so stressful she rarely ventured outside.

Coulibaly had found a spiritual mentor in prison, Djamel Beghal, who was convicted of plotting a 2001 attack against the U.S. Embassy in Paris. Counterterrorism officials consider him one of al-Qaeda’s top recruiters in Europe. As Boumeddiene and Coulibaly grew more observant, they turned to Beghal for guidance, visiting him repeatedly in southern France, where he was on supervised release.

Later, she put her foster sister in touch with him when the sister ran into a rough patch in her marriage.

“It seems logical to ask him for advice if he gives good advice,” Boumeddiene told police.

According to her account of the trips to visit Beghal, she also practiced shooting a crossbow into tree trunks. Photographs taken on one trip show her wearing a black full-faced veil known as a niqab, aiming the crossbow directly at the camera.

The couple also grew close to Chérif Kouachi, the younger of the two brothers who attacked the Paris offices of Charlie Hebdo, killing 12 people. Both brothers were killed in a police raid two days later. Coulibaly, who fatally shot a policewoman in a Paris street and four people at the kosher grocery, was killed in a separate Jan. 9 raid on the store, where he was holding hostages.

Coulibaly met Chérif Kouachi in prison at the same time he met Beghal. Boumeddiene struck up a friendship with Kouachi’s wife, Izzana Hamyd.

Counterterrorism officials say they are trying to determine the significance of the hundreds of phone calls in 2014 between Boumeddiene and Hamyd. One official said investigators believe that, at minimum, the wives may have passed messages between the men and that Boumeddiene was likely aware that something was being planned, even if she did not know the specifics.

Neither Hamyd’s attorney nor Boumeddiene’s former attorney responded to repeated requests for comment. Hamyd remains free, as does the wife of the other Kouachi brother, Said Kouachi. Both wives have maintained their innocence.

Pilgrimage to Mecca

In Boumeddiene’s 2010 conversations with investigators, she rejected terrorism but left open the option of fighting back against the West.

“When I see innocent people massacred in Palestine, Iraq, Chechnya, Afghanistan, where Americans send bombs and all that — and they’re not terrorists?” she said.

“When Americans kill innocent people,” she said, “it’s of course justifiable that men should take up arms to defend their wives and children.”

In October, Boumeddiene and Coulibaly went on a pilgrimage to Mecca. Investigators are trying to determine whether the couple met anybody with extremist links there. The investigators’ Saudi counterparts received no warning that a man convicted of having terrorist ties was visiting the country, a Middle Eastern counterintelligence official said.

When the couple returned to France, Boumeddiene hosted a celebratory lunch for 15 of her friends. “She was so peaceful,” one of the friends said. It was the last time many of them saw her.

Boumeddiene left France in the waning days of December, investigators say, eight days before the attacks began. Through a hole in the door of the couple’s final apartment, a crumpled green prayer rug can be seen on top of a laundry rack. Clean clothing hangs on the line.

Authorities say she drove from Paris to Madrid with Coulibaly and another man who had ties to terrorist networks. From Spain she flew with her escort to Istanbul on Jan. 2, then later made her way to the border with Syria, probably crossing over into an area controlled by the Islamic State.

Counterterrorism officials believe the logistics network has ties to al-Qaeda, a rival of the Islamic State — a worrisome sign that the two groups may have started to collaborate.

Now counterterrorism officials say they fear Boumeddiene’s position as the wife of a martyr may make her a powerful figure within extremist ranks. Some even believe she may return to Europe to carry out more attacks.

“We haven’t seen the last of her,” said Jean-Louis Bruguière, a former top French terrorism investigator.

Greg Miller in Washington and Cléophée Demoustier and Anna Polonyi in Paris contributed to this report.