That sounds exactly like my husband until we got the bed and mattress overlay. That's when he found comfort. He loathed the hospital bed with the alternating mattress as he found it incredibly uncomfortable.
Now, we have the temperpedic (ultra plush comfort), the overlay (specifically made for bedbound individuals), we put a pillow under his knees, and he wears the Stryker boots. He sleeps like a baby now, on his back, and says that he's never had a more comfortable sleep. I used to get up with him as often as every 15 minutes, but since getting all of the above, he sleeps 9-10 hours straight.
I hope you find something to make her comfortable. It's horrible when no one sleeps.