One thing you mom might consider is carrying a small towel or two that can be wet with cool water and placed on her arm if it gets too hot. I do this and once my limb has cooled down from the sun, I dry it off and place the wet towel in a plastic, zip lock type, bag.

Works wonders and extends my time enjoying my day outside.

As far as air travel, I hqve found that if I am able to move around the pressure change doesn't bother me as much as sitting still.

I hope this helps,
Best wishes,
Abbie