a bullet did, or many other far more sophisticated projectiles that defensive screens were designed to stop. Its relatively low speed in effect would "fool" the screens into treating it as a minor threat, since the screen could not see all that inert mass behind it.
However, the only possible advantage she could expect from an on-target arrow was one of surprise, in that Marvis would not expect her to have any weapon at all . . .
And there was Marvis! She came into view and into detection at the same time, flying slowly over the top of the cliff and not far i