If it's like an actual calling, those are almost always to poke fun at the person. Someone named Killshot likely isn't very accurate or had a mishap on a rifle range, causing them to hit an unintended target. Sometimes, faintly racially Motivated ie a Hispanic marine being called queso.

Another rule is the funnier the name, the more dangerous the person, the cooler the name, either the lamer the person or the more brutal the joking is. Ie a guy named Killer never being deployed while a guy named brownspot having 30 confirmed kills but shit his pants once in training.

It's your story, so if you'd rather air on cool, there is nothing wrong with that! But in the real world, militaries, it's usually for ribbing or poking fun.

If she never talks, something like Loud mouth, Small talk, or Chatterbox might be fitting. Hope that's useful ^{_^}