Gud if she wants to drive an older car so it will have more miles or hit a certain "milestone" that's her thing. She has a new car she can drive the new car. She can drive the old car to get it repaired.
If the car is unsafe and she decides to drive it knowing it's unsafe that is on her. That has nothing to do with you. You didn't make her drive the car. You aren't making her rack up miles on it. That's her choice.
She can also be all those things you said and be a bad spouse. Or at least not the right spouse for you. My parents have been divorced since I was 8ish. They actually have a very good divorce and are supportive with each other. Enough so that in short interactions people are surprised they are divirced. But get them together for more than 4 days and they push each other's buttons. There is all kinds of miscommunication going on and unspoken expectations of behavior that doesn't get met. Neither of them are perfect and they are good people they are just were not good as husband and wife.
I know we only get a small glimpse of what your life us like but no one is perfect and it's unreasonable and cruel to demand perfection frim a person.