I'm obviously not Sundrop but I'll throw in my two cents here as a former local.
Honestly, I'd say there's actually quite a bit of red clay? It's not everywhere, obviously, but there are plenty of places in the Berrien County and Irwin County areas that seeing it on a car wouldn't be all that strange, especially if you went down some of the back roads. A lot of the dirt roads seem to be made up of it; I used to go wandering down the dirt roads all around and lived on one when I was in Tift County and my poor Camaro would get coated in it after it rained, because it was easy to go sliding when the clay was wet.
Didn't she drive, like, a Mitsubishi GT3000? Honestly, I can't remember, but I could swear that was the car. Either way, I wouldn't see that car going offroad but it would definitely pick up mud/clay from dirt roads if taken down one, especially in some of the boggier areas where the roads never really dry out, out around Five Bridges Road and thereabouts.