There is a difference between a runaway teenager in a stolen car going 100 mph
who kills someone and a woman driving the speed limit who kills a motorcylist
because she didn't see him coming. And yes, prosecutors see that
difference. Depending on the circumstances the woman in this story would not be
charged with a negligent homicide.
I think that ANYONE who drives a car should have adult consequences if their
driving causes injury or death. If you are not mature enough to drive
responsibly and don't want to be treated as an adult, then do not drive.