Century Arms revolver in 45/70.Oh wait you said light.I'd sacrifice a little weight & go with the SS Ruger GP100 .357.Full lug 4 or 6 inch barrel in a cross draw holster.Or a drop leg when you have a pack on.I've got a 63 yo 5'2" woman friend who loves shooting my 6" GP100 with 158 gr.sjsp rounds so your GF shouldn't have any problems shooting it.Hiking in the woods you have to think about black bears also.Thats why I feed mine 180 gr rounds.Practice w/38s or 125 gr 357s & feed it 180s while hiking.IMO its worth the sacrifice in weight.
See my sig.
+1 what Tikigod said also.

SYKCO JYD#112
It's better to have it & not need it, than to need it & not have it.