Would the proper term be "gunwoman"? As in "I'm not a crazed gunwoman, Dad! I'm an assassin!"

"Well the difference be is one's a job and the other is a fetish!"

I interpret the text as analogous to "Kermit the Frog." She's a sniper, and her name is Girl.

It was recently confirmed in an official Valve comic that the Sniper's last name is "Mundy".

Now THAT's a knife!