What's her mobility like? With hand controls I assume she has a wheel chair and will have accessibility issues? Or have lots of friends who will have trouble with a low car?
Maybe something like a Matrix with a power seat that goes way up, up right easy access height seating, and the car ends at the rear glass.
Some long boat will be a parking lot nightmare and almost all sedans these days have poor rear view sight angles...
Also maybe a Chevy Orlando? Good visibility, stable on the road, not to high or low to get in and out of, lots of room for a wheel chair or walker?
My Grandfather bought my Neon and it wasn't a smart purchase in terms of accessibility, it was too low and 80-90 year olds could hardly get into the back seat.