Hi Idiopath,
It’s very possible or perhaps even likely yes. If her mattress isn’t keeping her spine and joints in good alignment in all her sleeping positions then it can certainly be a cause for back pain in the morning or can aggravate existing back pain.
No … there is no specific type of mattress that is more conducive to back health in general. Any type of mattress that is a good match for someone in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences) can make a suitable choice for those that have back issues as long as it keeps them in good alignment and relieves pressure in all their sleeping positions but the type of mattress or materials is a matter of personal preference. Every type of mattress or material has lower quality and less durable and higher quality and more durable versions so no matter what type of mattress someone may prefer it’s important that it uses good quality and durable materials so that the materials don’t soften, sag, or break down too quickly.
The mattress shopping tutorial here includes all the basic information, steps, and guidelines that can help with how to find the best possible choice in any budget range and post #13 here and the posts it links to includes the most important parts of the “value” of a mattress purchase that can help you make more meaningful comparisons between mattresses.
Phoenix