Hi StephenJ77,
Post #7 here and some of the links inside it will help you compare cotton to bamboo. While it can vary with the blend … in general bamboo is less natural, softer feeling, wicks moisture a little better, and in my experience isn’t quite as strong (but some would argue the other way around).
I would definitely use a mattress protector on a mattress both to help protect the mattress (and the warranty) from the moisture and body oils we emit each night and to hep reduce the effect of dust mites and the allergens they produce. It’s also more hygienic because it’s a lot easier to clean a mattress protector than a cover.
Post #89 here includes some of the pros and cons of different types of protectors. I would lean towards a top mattress protector rather than a full encasement unless your mom has problems with allergies and an encasement is necessary for greater protection against allergens in which case a full encasement with very small micron size pores (cotton or a microporous membrane) would be helpful.
Phoenix