She wasn't doing anything illegal, sure, but it was a bit reckless to arrange the transfer so that the buyer was expected to go alone, onto someone's driveway, to replace the license plates and drive off with the car without talking to the resident or owner.
Imagine if you sold your Magic cards to someone and told them, "oh, they're in my bedroom at 123 Elm Street -- just jimmy open the window and fish 'em out. If anyone asks, just give them this handwritten note."
Or, "Cool, just pick up the keys from under my office desk. Walk past security, just ignore them if they stop you, and fish them out of the cabinet. Pick the lock if you have to."
No. Bad idea. You look like a thief doing that.
Could they have handled the situation better? Definitely. But it's a bit much to act outraged that anyone would misinterpret her actions.