I don't see a problem with senior people driving provided they don't have any health issues that hinder their ability to drive safely. Just because you get old doesn't mean you can't still do things.
The article here said that the lady "inadvertently stepped on the gas instead of the brake". That's something that could happen to anyone. If she passes a medical test and shows that there isn't anything wrong with her physically, she should be allowed to retake the test.
Situations where the person has alzheimers, fainting, parkinson's, epilepsy or anything that could cause them to be less than effective / safe behind the wheel are a whole different story.
Years ago before I went back to school I used to work for a lawyer who was in his late 70's. He had advanced parkinson's where it was to the point when he tried to walk he would start by rocking back and forth and end up in an almost full run. When I left to go back to school that man was still driving! He drove me to the bank on 2 occasions and I feared for my life ... literally. In that case while he was still mentally fit, his body wasn't and he was a hazard on the road.
I remember looking after a man at work who was 99 years old. He looked to be about 60 and he even talked, moved and walked like he was about 60. He started to get chest pains occasionally and that's why he was admitted to hospital. It was the first time in his life that he had been sick since he was a kid. He still played saxafone in a band and he still drove. In his situation there was nothing mentally or physically wrong with him that hindered his ability to drive.
So age really has nothing to do with how safe a person is behind the wheel.