If she breaks down with the kids and calls you, go pick them up. Don't leave them stranded. But you're right. Her car repairs aren't your responsibility. If she thinks you're being a douche, so what? You aren't trying to be a douche, are you? You're just giving her what she wanted. A life without you. If she mentions it again, just tell her she should probably go get it looked at somewhere...
Me: 38 W:31 Kids: S16(mine from previous R), D10, S9, S4 M: 10 years T:12 years BD:Jan 3, 2018 W moved out: Apr 13,2018 Filed for D: Jun 2018 D final: Sep 2019