Driving is one of the hardest subjects to raise from far away, because the car is often where her independence lives. You can start with the car itself, since damage and wear are things you can see from your phone and discuss without making it a verdict on her.
Local option: New Plan Care gives families in the St. Louis area in-home help so a parent can stay home: companionship, help with bathing and dressing, meals, and overnight care. Call (314) 405-0887.
What the car tells you
Look for new dents or scrapes at the same height on the same side, mirrors that sit at a different angle than before, a bumper or panel that has been replaced without much explanation, and parking that is crooked or always in the same spot. Warning lights that stay on for weeks, or mileage that does not match the errands she describes, are worth noting too.
What to ask on a ride
Ask a local family member or friend to ride along on an ordinary errand, not a test drive. Have them note hesitation at intersections, drifting within the lane, trouble with left turns, late braking, missed signs, and how the driver seemed to feel about the trip. Note the route as well. If she avoids highways, night driving, or rain, that pattern tells you as much as a single bad moment.
Write down exact incidents with what happened and where. Avoid labels. A list of specific moments is far easier for a doctor or a family meeting to work with than a general worry.
What to do tonight
Ask a local contact to photograph the front, back, and both sides of the car, and to record the odometer reading. Then write down the last three times you heard about a close call or a new dent, even if she explained each one. That gives you a baseline you can compare against on your next visit.
What to leave with the doctor
Ask whether vision, hearing, sleep, pain, or any of her medicines might affect how she drives, and what a reasonable next step would be. Bring the list of incidents. Ask the doctor where the state licensing rules are published, since the state sets the rules and the doctor can point you to them. For ways to get her rides when driving is no longer the plan, see the Local Help for a St. Louis Parent page.