Why will nobody acknowledge our chief engineer is mentally ill?

The chief engineer of our Starship claims to be immortal and traveled around in space with some kind of doctor in a phone booth. Her crazy ramblings make no sense, she’s constantly making crazy comments about taking drugs in the 20th century. Nobody in medical nor the Captain seems to think this is odd which is incredibly concerning. They brought a new guy on board who seems to be doing most of the work, she’s not even showing up for most of her assigned shifts. What can be done to make sure she doesn’t accidentally kill is all while delusionally shoving garbage into the warp core because she thinks it’s a garbage can or something?