My takeaway: For little kids, be vigilant. And once your children are old enough to understand risk and danger, educate them to have common sense, while knowing that they will need help and supervision in getting there.
I put my arm around her and pointed to my eldest inside the van: "My son goes to kindergarten here. Why don't you come inside and warm up and we can figure out what to do next?" And then, just like that, a little girl I didn't know was sitting in my car.
Let me drop the mic on this situation right now: my daughter is more important than whatever is waiting on your work email, or however long the line at Starbucks will be in five more minutes, or the traffic you're going to have to sit in anyway.