Well, the ideal would be to have a vintage yellow roadster called Bessie, wouldn't it? Sarah's never owned a vintage yellow roadster, but I called her new (as opposed to classic) red Mini "Bessie" anyway.
Now she's got a red Peugeot 207, which I call Peggy. Just because I think "Peggy the Peugeot" sounds suitably alliterative.
I think Sarah would ideally like a black Pontiac Trans Am. No prizes for guessing what we'd call that, *ahem*.