Tia, what an interesting phrase. So the Belgians are older than she, and are soldiers? I am thinking this is more like tall tales, soldiers are telling lies or fibs that have little life or little truth. So tall tales is my guess, they are telling her stuff to impress her. Having been a young lass once myself I am well aware of the stuff young men say to young women to make an impression! Now if a native speaker would please concur or correct me!! Anybody out there? Marc? Frank?
Pam
"Leurs histoires vives" would mean exciting stories, with a lot of action happening, or at least described because it wouldn't exclude stretching the truth a little bit.
But "un peu" before an adjective and while talking about a story or something (or someone) you describe is also a way to mean "borderline" (and "un peu limite" is a very common way to say "borderline", without mentioning what kind of line you are crossing).
So, yes, maybe some parts of their stories were under the belt. But not necessarily. They might also be crude or violent. In one word, not grandma-safe.