Sweetheart of the Song Tra Bong: Believability

The Sweetheart of the Song Tra Bong is the only story in the collection I find completely unbelievable. There are details woven into the other stories which I question, but this story in its entirety seems unfathomable. However, for once it is not Tim O'Brien, the narrator, whose creditability is in the air. Rat Kiley tells the story, and even in subtle details of the language such as "the way Rat told it," give indication that even O'Brien does not take the story for fact, offering the idea there is an alternate, honest version buried away in history. The concept of an underage female even being able to navigate to a Vietnamese war camp is questionable, and the idea that the military higher-ups did not forbade her stay seems even more unrealistic. Details such as the necklace of tongues and the Greenies's cooperation with Mary Anne seem downright fictional to exagerate her love of the independence and equality she found at war. Yet Rat Kiley, a generally stolid character, getting emotional and defensive of Mary Anne give her character life. Maybe Rat Kiley fell for a creature of his own fantasy; Mary Anne representing the idealized version of the women he misses from back home, physically beautiful in a feminine way, but with the cunning mind associated with masculinity at the time. Alternately, it is not outlandish to once more question the reliability of O'Brien. Perhaps he embellished both the story told by Riley and his emotions whilst telling it.