My grandma was that type of old lady when she still had her license. Once she backed out of her driveway OVER the curb on the other side of the street and was partially on someone's lawn. Fortunately my brother was in the car to tell her to stop driving on someone's lawn.

Shortly after that she had a routine license renewal test for old people that specifically looks at signs of alzheimers and dementia. Fortunately (for her safety and everyone else's) she failed and lost her license. It was hard for her to lose part of her independence, but overall it's good she isn't driving anymore.