Jeff didn't really give her any time to think about it. She had to give him a decision in what, 30 seconds after he brought her car out? We've had time to consider every angle. With the excitment it would be hard to focus on "in the long run" thoughts so fast.
I also think that had she given the cars away, the winner would have given her the car back on their own. The winner of the money always gets a car. Tom got that ugly yellow truck. She could have said that as her final words when her torch was snuffed... "whoever wins owes me a car"