Let me preface what I'm about to say by emphasizing that I'm not excusing what this woman did. From what it sounds like she didn't even stop to see if the bicyclist was still alive. For all she knew he could have just been severely injured and possibly survived if she had gotten help.
Having said that, one reason people insist on driving even though they know they shouldn't is that in so many parts of this country there are few good alternatives. I had to deal with this when my mother could no longer drive. It's not unlike being under house arrest. In my mother's case she had some options but was too proud to take advantage of them or felt she couldn't afford them. I'm talking about the type of transportation available for people with disabilities.
Had she lived somewhere where taking public transportation was normal or where she was in walking distance of places of interest it would have been a different story. She might still be alive. The exercise alone would have made a huge difference.
As it was, she was isolated and dependent on others to get her places. We managed as best we could to help her but not being able to drive severely impacted her quality of life.
In that regard, we in this forum are ahead of the game.