In Wall-E's home, once Billy Bass starts singing, EVE points her gun at it. Since it's not living, it's harmless. Why does EVE try to shoot Billy Bass anyway?
Wall-E is not living. She still tried to shoot him. Several times. And that was just their first meeting.
At this time she is very "shoot first, then some more, never leave anything to ask questions to". She shoots or at least aims at any movement or noise source she detects.