13 Frightened Girls! (1963)

Like all of her classmates at Miss Pittford's Academy for Young Ladies in Switzerland, sixteen year old American Candy Hull is the daughter or ward of a London based diplomat. While all the girls can befriend whomever each wants at the academy, outside of its walls, especially back in the diplomatic world in London, they are supposed to associate only with those whose country matches their own's political leanings, which makes Candy and her best friend's relationship tenuous, she being Mai-Ling from China. With all the girls back in London on a short respite, Candy gets into some political intrigue when she stumbles upon some information that would have falsely implicated her father, John Hull, in a murder. Also knowing that it would save the job of Ambassador Hull's special attache (i.e. a spy), Wally Sanders, who Candy has known all her life and on who she now has a crush despite he being engaged to his colleague nicknamed Soldier, a code breaking specialist, Candy passes along the information to Wally only under the code name "Kitten". Wanting to help Wally further, Candy, reading up on how to proceed, embarks on a life of an amateur spy, she finding that no one would suspect an innocent looking sixteen year old girl in any political intrigue. With Candy continuing to pass along her foreign intrigue findings to Wally still only under the name Kitten, Candy may find that she has gotten in over her head in some countries seeking out Kitten to eliminate him/her, those countries including China. This situation places Candy's friendship with Mai-Ling in jeopardy, and will test the bond that existed between all the girls.