First of all, we need to get the story straight. Unfortunately the OP chose to post an article from Fox News, of all sources. The mother said she was only a few feet away but many witnesses actually said that she was out of sight of the car for more than 10 mins, like Bburky502 said as well. So does this change anyone's opinion of this mother?
Also, let's assume for a minute that we all agree that leaving the child in the car unattended was okay because she was nearby. What about the other things that she did wrong? First of all, she chose to park illegally in a loading zone. Secondly, she obstructed a police officer, behaving very badly when the police confronted her. Thirdly, she locked the doors, took the keys, and left her child in the freezing cold sleeping without heat.
I guess you'd be surprised to learn of all the cases when this happens. When I was 2 1/2 my mother, who was otherwise very responsible, left me sleeping in my car seat with the keys in the car while she ran in the house to get something that she needed to continue her errands. She was gone about five minutes. In that time, I woke up, managed to get out of my car seat, got in the driver's seat, and somehow ended up going into reverse until I hit the ditch behind me and the car stopped. Luckily, I was uninjured. But you can bet that my mother never left her children unattended again, no matter how nearby or where she was. And you can bet that I won't leave mine.
How do you know that the officer didn't try to simply have the conversation? According to reports, the big issue that led to her arrest wasn't neglect, it was the mother's behaviour when confronted by the police.
I guess when it comes down to it, that old saying, "Better safe than sorry," comes into play. Why take chances with your kids? For convienence?