It's possible that to her I sound like my father. Putting her down for buying the wrong car; putting her down for driving it poorly.
Yet I really do believe it's the wrong vehicle for her. She's so weak now that she struggles to turn the wheel. She struggles to shift gears, she struggles to see through the defrosterless windshield. She drives at 40mph on the freeway, where she's a hazard to herself and to everyone who encounters her. Backing out of her parking space is so exhausting that she has to rest.
I suspect that she'd do fine with automatic transmission, power steering, and a working defroster.
Still, as she insists through her peremptory tone, it's not my decision.