Plenty of cars can make that trip on one refueling stop. And if she's worried about cameras just pee by the side of the road somewhere: it's not that hard.

She's probably more an Evil Lunatic than an Evil Genius - I don't see this is a case where it's necessary to search for a rational explanation for her every action when there probably isn't one.
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"If they can't picture me with a knife, forcing them to strip in an alley, I don't want any part of it. It's humiliating." - windsock