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If she feels best behind a salt truck, who cares? It's just a freakin' car. If it gets dirty, waash it. If it gets a few chips, well, so what? Are you saving it for the next owner?
You should have counted to ten and then had her haul out the garden hose and thoroughly wash the top, wheel wells, and underside with fresh water.
Just slide a garden sprinkler beneath it and let it go for a while.