LOL.. that sucks. My wife is almost the same way but she knows what gas i put in my car. I share because she actually buys stuff i want for my car, and she also has a nice car also so i dont mind driving it.
I have come to a conclusion though. Once the wife drives the car, be ready to do an extensive cleaning. i thought getting her a 2007 40k car would make her take care of it or would want her to keep the interior somewhat clean..YEA RIGHT!!! Didn't work. Right now her brand new car smells like onions because of the left over lunch burger that stayed in the car for a day

and she never rolls down the windows. A/C ALL DAY!!! Can't mess her hair up..lol.. i still love her though.