Bad Steering you refer to comes from the need to constantly correcting the steering wheel when driving on highways. Over 60 mphs or so those donnut fat stock tires on my 2013 Corolla L 15" steel wheels have no sense of direction and it starts to wonder around. This was very "tiring" on my shoulders, for the lack of better word and causing a lot of safety concerns!
I replaced the tires/wheels with 16" 205 wide low profile Yoko AVIS and some light wheels I had around. Problem solved for me. No more wondering and much more secured ride. My shoulders feel whole lot better. I think it even improved my seat comfort from not having to adjust my body when it wondered around.
Corollas are built on light frame and could also use some metal braces for better handing. Next up for me is front strut bar, rear sway bar and lowering springs for better center of gravity and improved feel and handling.
I was pleasantly surprised when it returned 36 mpg on the second tank thou, on mixed driving! But, it seriously need updated tires/wheels combo. I don't want to drive under 60 mph just to keep my steering straight. There should have been some recall on this serious issue long time ago!!!
It also probably needs better alignment.
Funny thing is my third gen Prius w/ stock 15" wheels/tires never had this issue. It sped along 80+ mph w/o any issue. It was one of the most secured feeling car on highway...
You get what you pay for from Toyota, I guess.
I'd recommend a base Prius for your mom. Much better built car with kick ass gas mileage and a safer car!