If I lived closer,I think it'd be worth spending some time there getting an inventory and actively marketing some of the more valuable vehicles,in exchange for a few for myself,or a small percentage of the sale profits.
I'm still thinking of the museum idea-why wouldn't that work? Might have to move some of the cars to make it more accessible,but I'll bet it could work. I don't think zoning would be an issue,and if she continued to downsize by selling cars as possible,so much the better. At least,as a museum,she'd get a bit more time to move things out.
Speed