"You'd be the first to know."

It's not phrased as reassurance, nor does it reflect any awareness of how much Bryce is able to glean from other sources; just a fact, and also a 'no'. For the person doing the shooting, that could mean going unnoticed, or it could mean provoking something she can't hope to match. It's with a sort of resignation, neither brave or suicidal, that she doesn't pause to think about it.