Hi StephenJ77,
Just in case you haven’t read it already … the first place I would start is post #1 here which has the basic information, steps, and guidelines that will be most helpful.
Some of the better options or possibilities I’m aware of in the Charlottesville, VA area are included in post #3 here.
Since your mom is used to sleeping on latex I would probably include some latex options in your research because it can be difficult to adjust to the feel of a completely different material when you are older and used to something completely different. If she has had the chance to test both she will probably be able to give you a clear indication of whether she prefers a slower response (memory foam) or faster response (latex) material. In some cases memory foam may restrict movement more than she is comfortable with but her own personal preferences would be important. Either one in the right design can provide her with the best balance between good alignment and pressure relief that are especially important for someone that is facing many health challenges and may have clear preferences no matter what others may find works best for them.
You can see some of my thoughts about bedinabox in post #2 here. They don’t use particularly high quality materials in the upper layers of their mattresses (the memory foam) if durability is an important part of your choice. Some of the better online memory foam options I’m aware of are listed in post #12 here.
One of the most important parts of a successful mattress purchase can be the knowledge and experience of the retailer or manufacturer you are dealing with and if I was in your shoes I would initially focus on talking with some of your options on the phone and letting them know what you have posted here and talk with them about what they carry that may be worth considering before you actually visit them. The ones that are only interested in having you walk through their front door without providing you with any information at all or without regard to whether they carry something that may be suitable for your criteria are the ones I would tend to avoid. I would also make sure that they are able to disclose the specifics of what is any mattress that you are seriously considering including the thickness and density of any memory foam or polyfoam layers and the type and blend of any latex. Better retailers and manufacturers are much more comfortable talking about materials than the ones that only like to give you marketing information and are more focused on selling you anything they can instead of educating you and helping you make the best possible choices that fit your personal criteria. If you do much of your preliminary work on the phone first you will save yourself (and your mom) a great deal of time, will avoid testing mattresses that you may like the “showroom feel” only to find out you can’t find out what is in it, and will have a much better sense of which retailers and manufacturers have the knowledge and experience and the selection that you need to make good choices.
The adjustable bed thread here also has some helpful information and includes some links to retailers that I use as a “value reference point”.
Phoenix