Islamic State's lasting grip is a new hurdle for Europe, US

The girl, speaking in the lilting accent of southern France, appeared in government ads describing how she was recruited by Islamic State extremists during her quest for religion, then encouraged to quit school and go to Syria, and finally to plot a suicide attack against a synagogue at home.

"I have a hard time even admitting now that I was indoctrinated," she says to the camera in the ad before breaking down, describing how she tried to recruit others.

The teen, known as Lea, was meant to be the poster child of a nascent program in France aimed at de-radicalizing young people to stem their flow to Syria. But the jihadi rehab didn't work. Six times she reconnected...