And on that same note, one of my relatives by marriage discovered that they were dyslexic while completing a master's degree that involved analyzing brain imaging -- of dyslexic persons. Up until then, they had compensated quite effectively by using their exceptional oral language and social reasoning skills to absorb content by listening, and to talk their way out of all lengthy writing assignments.
(FWIW, that's also how my color blind parent learned he was red-green color blind--in medical school, while learning about color blindness.)
One of the factors contributing to distress for learners with focal disabilities is the awareness of the gap between what they "should" be able to do and how they actually perform. This occurs commonly for learners of generally average ability who have specific learning disabilities, but since, in my observation, the magnitude and nature of the gap is far more critical than the absolute level of performance, the intensity of this distress can be correspondingly far greater for gifted learners--even those who are also high performers.
Your DC has clearly not reached her true instructional zone (on a purely academic level) even now (or she wouldn't be maintaining all As while routinely procrastinating), which suggests that her true potential is far higher than that implied by two years of acceleration. That doesn't, btw, mean that this is a flawed placement. In fact, it appears that it is exactly right for illuminating growth needs in some other areas that will likely be crucial to her long-term health and happiness, while not also penalizing her academic record. But the point is, the gap between her internal feeling of what "should" be easily accomplished and the amount of effort she puts into accomplishing it may well be significantly larger than it appears from the outside.
