I’d tell her to buy a .38, then upgrade to .357 Mag when she gets comfortable with it.
I’d say buy a 357 Mag revolver and then shoot 38 special out of it until she’s ready for the .357 mag ammo. So she wont have to buy twice.
But having two pistols is also good.
Actually the NRA recommends a .22 Magnum for a woman. Not so much recoil and a much better pattern.