I would still bet on something other than the Pt being the problem.
Such as simply moisture trapped under the ring.
Most Pt solders have little Pt content, so the high melting gold
solder is perhaps less likely reactive than non plum Pt solder!
I would suggest she tries wearing an inside round "comfort fit" Pt
band for a while. No reaction / Pt is not the problem. A reaction and
yes the Pt band is the problem.