Nor was there ever any indication that she was in charge of engineering as a whole. She seemed to be the senior officer in the particular subsection of the engineering complex that was responsible for the dilithium circuits, but that's all.
...Perhaps in charge of just dilithium crystal re-amplification, even? It sounds like a rare procedure, and might call for a dedicated blueskirt specialist working with special equipment somewhere far away from Scotty's little kingdom.
It's nice to have two speaking Starfleet parts down at the facility where the Lazari do their raiding - and it sort of makes plot sense that this facility be a small, isolated, never-before-seen one, because the heists would have been much less plausible down at Main Engineering where Scotty generally has plenty of assistants around.