Would it not make more sense if Vayne's Bolts were made out of Petricite or Demacian Steel?
Considering Vayne has dedicated herself to hunting down users of magic as well as magical creatures, how come she doesn't utilize magic nullifying metal?
I know Silver is supposed to be good against Vampires and Werewolves in normal works of fiction but as far as I know, Silver has no special properties within the context of the League of Legends universe itself.