If she has the standard flimsy innerspring mattress a good upgrade would be a Solace foam mattress. A low-air-loss inflatable one could be a good choice as well especially if sores are an issue. The gel topper previously mentioned would be an improvement for sure. Her doctor shouldn't have a problem prescribing one so insurance will help cover the cost.
As I go through life I keep coming to the same conclusion, people are generally stupid.