Earlier on my mom would press her heals hard into the mattress at night. She started to get pressure ulcers on the back of her heals. We had to get special boots for her to sleep in that supported her heals off the surface. Maybe watch them carefully for any signs. Mom's had damage inside before it showed on the surface.
But Seroquel can make you lightheaded and she could have fallen or twisted her ankle. A simple XRay would show if anything is broken.