I have found that a few 10penny nails are a very effective way of discouraging this sort of slob. If she had to take transport to get where she as going, a nail angled so that each tire would puncture itself as the creep backed out would start a leak and still allow the person to leave the lot prior to deaeration. It might take a time or two but eventually the message will reach into that dim mind that their behavior was undesireable.

Let the punishment fit the crime.