+ Dose bleach nightly.
+ Add CYA via a suspended sock.
+ Don't add salt to a AG pool, unless you don't care about the warranty . . . and are pretty sure your pool will survive the added corrosivity.
+ Borax is supposed to have some effects like salt, without as much corrosivity. It would require ~7 boxes + several gallons of muriatic acid, if you want to pursue that, but there's no guarantee it will help.

BTW, sensitive skin tends to equal non-oily skin. If she'll rinse off with fresh water as soon as she comes out, and then apply lotion, it will probably help. (My wife taught water aerobics for 10 years, so we know the 'tricks'.)