I have pretty much the same thing. I got pretty familiar with the two pieces in therapy. My last therapist couldn't tolerate the cold, sadistic piece but I had no other way to "express" her point of view than to "be" her. At least for starters. Seems like a specialist in dissociative disorders would have understood that but she didn't.

However, despite my last therapist's rejection of "her", I can now accept my cold, sadistic piece -- just so you know (and don't have to be afraid of me?) "I" have pretty good control and "she" doesn't usually "be" or "act out" without "me" allowing it.

So, I'm also willing and able (I think) to "hear" what your sadistic piece has to say, if you want to try that.

I'm familiar with and accept my "better' piece, too, which I think of as a self-loving narcissist -- me, first! But not particularly against anybody else, unlike the "darker" piece.