It sounds like she is talking about splits, which is unintegrated parts of your ego or sense of self.

Its the same as dissociation, imo, though people often talk about dissociation as a process, whereas your therapist is psychoanalytic so might think of it more as splitting.

That concept goes all the way back to Freud but just gets renamed or reconceptualized according to different schools of thought.

I think of it developmentally, as infants have simple, black and white emotions or states-good vs. bad, hungry vs full. Complex emotions dont develop until later. So when the psyche becomes too overwhelmed, consciuosness gets split off as a way to cope. If it happens over and over, it becomes part of your cognitive style then personality.

Consciousness overwhelmed is equated with trauma, by some schools of thought.

It does get integrated with the type of therapy you are doing. It can really be destabilizing when you are integrating those parts. Its very difficult, but you are on the right track.