I may be wrong, but I don't recall these tragedies being anywhere near as common before it was required that children be in the back seat.
This woman is responsible.
Of course she is, and she will rightly blame herself for the rest of her life. But still, this probably wouldn't have happened if not for the government regulations.
You said, "...this probably wouldn't have happened if not for the government regulations."
We rode in the front seat as kids in the 70's with no seatbelts. If my mom drove off the road, hit a tree, and I was thrown from the car, then who's responsible? Not the government for sure.
The mother didn't pay attention. End of story--no excuses. Own up to what she did and face the consequences.
If you leave an animal in a hot car you can be fined. Why would you not make a person responsible for the death of another human being? Where do excuses end and responsiblity for one's actions begin?
Not only are they in the back seat, but young children are reversed - facing the seat.