I was more thinking the traumtism itself. Alledgedly someone's hair can go full white in a couple of weeks after a brush with death but there's scarce scientific evidence on the subject.
I guess her vocal cords have been damaged and partly replaced by a troll's resulting in a wonky voice.
Unless Xykon or Redcloak told somebody off-screen, no-one knows. Honestly it seems like Lirian and Dorukan had a happy ending so I'd doubt we'll ever see the gem again, except maybe if it is destroy during the ending.
Maybe she went gray late in life then. Or maybe halfling biology is different.
So any halfling can live naturally to [105:200] years old? Seems like brown hair by 80-100 is justified.