How do I keep elderly with bed sores on butt to stay on her side?

Ask her provider about ordering an alternate pressure mattress if she doesn’t already have one. They can be rented but hospice should arrange for one to be sent to your home. That will help some but she will still need to be turned every 2 hrs.

I'm sorry you're dealing with this, PMorales. We ordered a foam wedge pillow on Amazon (the one we ordered is called the Positioning Wedge and was about $30) and it props my father up very nicely. Also, when we used to have to turn him a few times in the middle of the night because of a pressure sore, just getting that wedge pillow wedged in there made things so much simpler in the dead of night when you're half asleep and just need to get it done (with the details about proper positioning that AlvaDeer described) and get yourself and your loved one back to bed and sleeping. We put a regular pillow case on it. I can imagine there would be problems with soiling with someone who is incontinent (not an issue with my paralyzed dad).

It sounds like you are in a hard spot right now. Blessings to you and your family.

THEY should be teaching you to do this. What's the matter with them! It is awfully difficult to describe, but basically you turn her to her side. Then you be certain that the top knee is raised fairly high; this tops the body even MORE to the side it is turned to. Then you take a good pillow, one that is malliable, and you wedge the edge of it under her back, kind of bending the pillow side closest to you back under the pillow so that it is almost a "roll", like a foam roll. Some people use foam rolls, but they often end up soiled. If she is small and you are strong you can put two flat hands under her hips and kind of pull it toward you so that her body kind of bends as though resting in a sleeping position.
Take careful note of how you sleep. When shoulder and arms and hands are, hips and legs. This gives you a good idea of position of the body. You might look on you tube. Seems to me they have a film for everything and body positioning is likely there. All that said, these folks can then make a liar out of even the best nurses and get on their backs in a second. You are stuck with foam donuts and things them to keep that area off bed, but never a good answer with that. Sores are awful to deal with. I am so sorry. There are times, in all honestly that you can do almost nothing.

Please ask your hospice nurse to show you. You can use pillows, foam wedges. But hospice should demonstrate and get you what you need.