And to actually address your question - in addition to his crazy VCI/processing speed difference, DS was diagnosed with dyslexia and dysgraphia. Based on what I've learned about dyslexia/dysgraphia - it's really a full-on difference in brain wiring. So maybe it's all of a piece.
Anyway - has your daughter had a neuropsych work-up that would look at these things? Having this data has given me some additional patience in dealing with these challenges, as well as providing better focus on which strategies are more likely to be effective.