She uses a walker, sits on the side and cannot get them up. She has a bed bar which prevents her from falling out in the process, but that doesn't help her actually get her legs up. Sometimes she can get one leg up enough to use a heel to push her self further onto the bed. Sometimes she can lie on her side and bring them up to a fetal position with the help of the bar to steady herself. Would some kind of sling help? An adjustable bed?
My husband and my mother both loved a hospital bed and there are good advantages to the adjustability. I'm not sure how the height of the bed impacts the strength of the legs, though. Maybe it is less effort to bring the legs up a short distance than to a higher bed. If you explore that route, be sure the height of the bed is controlled by the patient. On my husband's bed that was on the foot of the bed and not on his remote device.
If you come up with a good solution, post it. We learn from each other.
Now I checked my guest room bed, no luck, it has a very thin metal frame that would hurt one's feet.