One of my secrets also is to keep the wife in a car she likes. If she's happy with her ride there's a much better chance she won't worry about yours and/or feel jealous. You've got her in a Sentra? I'd be PO'd too! She's taking it out on you!
I've encouraged my wife to drive the 370 and she really likes it. She learned to drive on a '59 Chevy with a 3 spd column shifter so she can handle most anything. She's also really practical so her Element suits her just fine. She's happy, I'm happy.....