Hi lumy,
It certainly sounds like you and your mom are zeroing in on a mattress and she already has ‘crossed out’ certain materials and mattress types, that’s’ great!
As far as the ‘big box’ stores, I would say to keep in mind the Mattress Shopping TutoriaI as theMattress Specifications You Need To Know and the Mattress Durability Guidelines
And I personally avoid any mattress that does not provide full specifications for their products, as this sometimes hides inexpensive materials or excessive amounts of lower density foams. Also things like copper infusion and such can be a ‘marketing gimmick’ which I am dubious of. Gel foams have their own pros and cons, I would be wary if there is no density (lbs/cubic ft) or layer thickness provided, as, again, some companies hide inexpensive and lower density foams in their products. Since this will only see use for half of the year, and it sounds like your mom is favoring latex, the important thing is that she enjoys the feel of whatever she decides. Hopefully Bay Beds can set you up with a mattress your mom will enjoy, especially with your increased budget.
Let us know what you finally choose and how it’s working for your mom once she spends some time on it.
~ Basilio