Which angel are you?
To me it was crystal clear that this was the wrong thing to do. She should rather have driven him all the way,a nd if the kids would have been late, they could say it was for the sake of an act of chesed. That's positive chinuch in my view, as opposed to the model that says you only help someone to the extent that it doesn't inconvenience you. But I got a number of reactions that said I was wrong, and the mother may have been right because a delay to school entail bittul zman Torah for these kids under 7. That line of reasoning is wrong halachically as well as hashkafically.
Here's Rabbi Frand's take on a parallel situation in his piece entitled G-d’s Plans Will Happen
What that mother was showing was how to be a bad angel -- the one who says I care about my kids' coming on time to davening more than helping a fellow Jew with a broken leg get to where he needs to go. I'll help, but only half-heartedly and halfway.
Related: post on Vayeshev http://kallahmagazine.blogspot.com/2015/12/reuvens-motivation.html