Or her usefulness to the episode could be that Edgar Alien Perv has a crush on her.

Yeah that was a super rough episode.

We just are taking two different perspectives about being essential. Uhura was like an organ: quietly essential to the regular operation of your body. Whereas Hoshi is like hands or maybe ears or something: very important for achieving your body's goals, but you can compensate for them not working. You're right Uhura is more essential. I just think it's more interesting watching the hands / ears of the ship helping achieve the mission.