My own experience, which is not really so much over but still in progress, is that "that girl" that holds certain memories has got kind of a sassy, attention-getting side to her. I can either treat her with respect (and compassion) and experience a sort of gentle release of a specific memory, or I can be dismissive and hostile towards her. The later results in her pretty much tossing stink bombs (e.g. bad nightmares, unpleasant olfactory or other details that make me feel sick, or really scared, or, well, you get it) at me until I actually get it through my thick skull that I need to BE differently towards myself or ain't nothin' going to change.

Consider that maybe these nightmares are not just "information" about facts in the traditional sense, but their method of unpleasant delivery is also information that you may want to pay attention to. However much you may hate "that kid" for what you think she did wrong or didn't do right, she's got a certain amount of agency now and she's not afraid to F you up with it. For me, having some realization that "that kid" had actually evolved in the 40 some years that I the adult have evolved, or that she had benefited from therapy, that she had the stones to try to mess with me to get my attention, was pretty much the beginning of me getting some perspective on who I was as a child that didn't involve detesting her.

Anyway, I have no idea if my experience has any resemblance to the neighborhood of what is going on with you, but I think your T makes a lot of sense that changing the current situation is about changing the way you see/saw yourself as that kid.