I'm a rank amateur and can't comment on the technical whys and hows of exposure compensation whilst shooting dark and light subjects together. My initial reaction was that the framing looks odd due to the distracting background, specifically the black object screwed to the wall that demands almost as much attention as the woman. I'd suggest first and foremost thinking very carefully about the composition and background of your portraits (unless there's a creative reason for the metal thing, in which case apologies!).