Depending on what the problem is, she might try various regular chair cushions. My grandmother was "small framed" and the car seats were ucomfortable. She tried all sorts of car seat cushions with no luck. She ended up using a regular chair cushion - added ties to the back corners to attch it to the car seat. Made all the difference in the world for her - gave her a slight lift so her back fit against the back of the car seat better.
Mentioned it to a custmer who was looking for a car cushion and she tried it and found it to work perfect.
