From Team Fortress Wiki

Miss Pauling responses are contextually triggered lines that play after a player receives or completes a Contract during the Gun Mettle Update or Tough Break Update events. All of her lines can be heard below.

Lines are only triggered when the player is connected to an official Valve server. Decoding a new Contract while connected will trigger a line based on the player's current class, regardless of its actual content.

Gun Mettle

Contract related

New Contract

Contract progress

Tough Break

Contract-related

New Contract