So sweet of you to do this for her. Is no one gave her a small pillow you may consider that also. I had Mother make small pillows to go under my armpit while I was healing and a bit larger to fit under the seat belt of the car. Those items that wrap around the seat belt are not cushiony enough. Often folks make a heart shape 9" or so pillow. Those fit up under the armpit and in front. Ahhh, I remember how much the pillow helped while my body was healing.
Prayers for both of you.