"Among minors, females are over-represented to a proportion of 55 percent" of those interested in making the journey, or who have already done so, the French source said on condition of anonymity.
Like young girls across Europe who dream of reaching Syria -- and often leave their unsuspecting families shocked when they do run away -- these girls are not just dreaming of becoming meek so-called "jihadi brides".
While marriage to a jihadist fighter is their likely fate, the girls are as attracted by violence as their male counterparts, said sociologist Farhad Khosrokhavar, who has interviewed many radicalised French teenagers of both sexes.
"Previously, violence was almost exclusively a male phenomenon (but) this generation has a different outlook," Khosrokhavar said.
"I have spoken to many who say: 'My ideal is Kouachi'" -- the surname of the brothers who killed 12 people in an attack on the offices of Charlie Hebdo satirical magazine in January last year.
"They don't want to be his wife, or his girlfriend: their dream is to be Kouachi himself."
However the complex road to radicalisation, during the fraught teenage years, has many sides to it, and one does have to do with sexual attraction.
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Khosrokhavar said many of these girls were tired of the "immature young boys" around them in the West.
"There is a new cult of heroism, of virility. The young jihadist becomes a masculine ideal for these teenagers... it is an anti-feminist post-feminism: that is, they want a man with traditional masculine virtues."
'It is like punk rock'
British researcher Erin Marie Saltman, author of "Till Martyrdom do us Part", a report on the role of women in Islamic State, says many of these girls are also drawn to the humanitarian arguments of recruiters.
"It would be wrong to consider these women just jihadi brides -- their reasons for going over are much more diverse."
Saltman, of the Institute for Strategic Dialogue, said many girls truly believed the Muslim population was being persecuted and they were part of an effort to "create security and a future for Muslims around the world."
"It is almost like a sub-culture. It's like punk rock, it's against the system to be joining this deviant movement," Saltman said.
"So although we see it as a very conservative, chauvinistic, oppressive movement, this is actually being interpreted by people involved in it as being like an underground social movement. And that appeals, of course, to teenagers."
Saltman's report says more than 550 women are believed to be among an estimated 4,000 Western foreign fighters with Islamic State.