I'd actually avoid anything designated for hospital use. Always hard and sealed for infection control. Price the air inflatable type, that way you can be sure she'll be comfortable. I'm sure you know you need padding where bones are close to the surface to avoid skin breakdown. (elbows, hips, coccyx, heels).
It's great of you to do this. "Who is caring for the caregiver" is a hot topic in healthcare now.
"The problem is not the problem. The problem is your attitude about the problem. Do you understand?" Captain Jack Sparrow.