She needs a referral to adult social care for a proper assessment. I wouldn’t worry too much about the cards, it’s the type of thing she could still be doing with support. It just needs someone to take her there and back and a member if the club to be willing to ‘play’ with her, sometimes just being in the social environment is enough for it to feel ‘normal’ for people with dementia. I would advise reporting to the DVLA immediately and remove access to the car. This is non negotiable, tell her it’s broken, in for a service, waiting for a part, whatever.