Am I being unreasonable? #1

So I pay for my wife's car insurance and my name and hers are on the title. She lets her 18 yr old kid drive the car all the time to school and work. My concern is that the kid is not insured under us or on her own. Wife says is ok and I say its not. I also pay for gas for wife to drive not her kid who has two jobs and lives on her own...this causes fights because I dont agree! Am I being unreasonable?