My mother is 78 and although not officially diagnosed, I believe she is in the early stages of dementia. Her primary care recently prescribed Aricept but I have not noticed any difference in her memory or recall. She suffers from carpal tunnel and has a hard time using her right hand. In addition to all of this she has been having dizzy spells. She will not tell me the truth about how she is feeling because she knows I will tell her she can not drive. I have already restricted her driving to 2 major streets near our home that she can get to most everything she needs. Otherwise she gets lost. But I no longer feel that these 2 streets are safe with her on them. Up until recently I would have her drive my mother-in-law to the Council on Aging for exercise class on Monday morning (they both live with me) but no longer allow that because if they both got hurt in an accident I think I would lose my mind. I am pretty sure if she took a driving test she would pass because she would focus only on driving for that short period of time, but otherwise she is a very distracted driver. She has had many dings and scrapes on her car and has spent lots of money to repair them because in her mind if she can't see them they never happened. I have tried going through her primary care and he just offers up the driving test. Any thoughts??
Has your mom gotten lost? Has she gotten tickets?
Not to say that you couldn't have your own rules about the circumstances under which you will allow either of them to live in your home. You could require that they not own a car, that they not drive or ride with dangerous drivers as a condition of living in your home or you being their caretaker.
Obviously your mom listens to you or she wouldn't restrict herself to the two streets (or does she?).
It's an important issue. I'm not trying to make light of it but if the prevailing authorities find her competent then you might have to accept that for now.
If you feel a passenger is distracting and it well may be, then begin by finding an alternate transportation mode for MIL and asking your mom to drive alone. Make time to take your mom on her regular trips or find a driver that can help out.
There are many threads on this site on seniors driving. Use the search and you can read about others experiences and solutions.
It's very depressing for a senior when they have to stop driving. Failing the test might be upsetting but at least it would be from a recognizable authority and easier to accept than from a daughter.