All evidence points to Marvin having once lived in close proximity to humans. However, evidence also point to her having been abused by humans… not least of which being the two BB’s. However, there’s something psychological as well.
When I surprise Marvin, such as by coming into a room unannounced (especially when it’s dark), she’ll hiss… but then she gets over it and is friendly in a hurry. But if I’m holding something like a sock, a belt, suspenders… she hisses, freaks out, runs and hides. Something about the image of something long, thin and floppy disturbs her greatly. I hypothesize that someone went after her at least once with something like a leash or a belt.