Three Hours In Paris by Cara Black 

Kate Rees, a young American markswoman, has been recruited by British intelligence to drop into Paris with a dangerous assignment: assassinate the Führer. Wrecked by grief after a Luftwaffe bombing killed her husband and infant daughter, she is armed with a rifle, a vendetta, and a fierce resolve. But other than rushed and rudimentary instruction, she has no formal spy training. Thrust into the red-hot centre of the war, a country girl from rural Oregon finds herself holding the fate of the world in her hands… Read more.