Brandy rear-ended a car whose driver DIED.
There is a middle step you are leaving out. Brandy hit the car, the car was pushed into another lane and then hit again by a different driver.
I haven't heard it suggested that is was the rear-ending which killed the woman. Brandy wasn't drunk or drugged, no one has said she was being particularly reckless. She was inattentive, obviously. If you've never had a moment of inattentiveness while driving, congratulations.