A relative dip in PSI happens with some students with ADHD, but it can also be due to quite a few other things, or it might mean nothing at all other than a relative weakness in abilities. The tricky thing is that there are other types of challenges which can appear to be inattention when they aren't recognized and accommodated. Has your dd been through an actual ADHD evaluation (which would include behavioral surveys for parents and teachers, plus possibly other types of tests of executive function and attention)?
Best wishes,
polarbear
