At a recent show, I saw the car seat double as the seat for the wheelchair. The frame of the wheelchair was carried separately. And the whole seat moved in and out of the car electrically. Well worth getting along to a Live event when one is near you, whereby you can get all touchy feely and try things out / ask questions etc..
I have no experience of such things. But here is an example.
Best wishes to you and your mum.
Skoda Enyaq Race Blue