This is totally asinine.
I use to leave my son in a locked car every morning before going off to work. I take him outside, put him in his car seat, then lock the car and go back inside to grab what I need for work. My biggest fear has always been some stupid neighbor or stupid cop thinking my child is "in danger" because he's strapped into the seat on a chilly morning in a locked car. The time limit in California for leaving a child unattended is 3 minutes. This was in Chicago, but it looks like she was within 30 feet for about 2 mins.
This is the type of stupid shit cops should get heat for. This guy wasn't enforcing the law (she was on her way back to the car when he stopped her), he was acting like a jerk. So now they might throw her in jail for a year and fine her. Yeah, that'll make the kids grow up so much better not having a mommy for a year. MORONS!