MOSCOW — Baby-faced, she looks barely a teenager. But the pistol she is holding in the photograph suggests the violent destiny that she would choose: blowing herself up in a subway station in Moscow during the morning rush on Monday.

And posing with his arm around this 17-year-old woman is the man who would put her on this path, a 30-year-old militant leader who lured her from her single mother, drew her into fundamentalist Islam and married her. He was killed by federal forces in December, driving her to seek revenge.

On Friday, as the photograph circulated widely, the couple turned into an unsettling symbol of Islamic militancy in Russia — deeply repugnant to most people but also likely to be embraced by other extremists as a propaganda coup, a kind of Bonnie and Clyde of the insurgency.

The story of the woman, Dzhanet Abdullayeva, from Dagestan, a volatile, predominantly Muslim region of southern Russia, near Chechnya, speaks to the challenges facing the Kremlin as it vows to stamp out the armed underground. Harsher measures can backfire, further radicalizing a population alienated by endemic poverty and corruption. And men are not the only threat.