Mostly my DW just uses me in that instance.
She's just under 5' tall, we carry one of those fold up steps so that she can reach the fan if needed. https://www.amazon.com/Rubbermaid-RM...s=folding+step
Most of the time it's in front of the passenger seat, otherwise her feet just dangle since she can't comfortably reach the floor.
Your DW, if like mine, is quite adept as using something to give her some reach. I told mine I'd cut a slot in the end of a wooden spoon so that she could use it to turn the crank. And with other end she could push the button. She liked the idea, but likes having me do it even more.