Mom doesn't need / won't use hospital bed but she does need a bed that's 21 inches high and head can be raised. Any recommendations?

Look for adjustable beds.

I got my dad a full size adjustable bed that moves very similar to a hospital bed but, it has massage features as well.

It was pretty expensive. Oh and it weighs a ton, it takes 3 strong men to move it.

I just received a flyer for sleep number adjustable beds. Those are really nice beds and can be put on low frames.

Just have to do some Google searches.