Hi Moody.
Welcome to our Mattress Forum. 
It would be nice if we could just “accio!” the perfect mattress, right?
, this article on [url=https://mattressunderground.com/mattresses/comfort-layers/buckling-column-gel]buckling column gelI’m not sure where you are in your research so just for easy access, I’ll leave our (in the Purple mattress), and this one about latex as a comfort layer for your perusal.
Additionally, the Mattress Shopping Guidelines may come in handy.
What is it she likes best about the Purple 3? As per our article on buckling column gel, it’s meant to be a very durable material and while it has not been on the market long enough to know this for sure, a reasonable expectation is that is should last as long or longer than most other materials on the market. But, this is all guesswork.
Arizona Premium doesn’t do full returns on DIY components but will do a layer exchange within 60 days if the ILD of the foam isn’t quite right.
Arizona Premium recommends these covers while Sleep EZ (similarly) recommends these.
Ultimately, all other bedding is really a personal choice. There is more information about comforters in the posts and topics that are linked in post #3 here .
There is also more information about the different types of sheets and bedding in post #7 here and the other posts and sources of information it links to that should be helpful as well.
I hope this helps!
NikkiTMU