I think being more 'matter of fact' about some stuff has helped with our ds9, but dd3 is another story. Hopefully some of her full throttle attitude about a lot of things will relax when she is older.

It may be about intellectual control/independence (as someone above suggested) vs. emotional needs that don't line up (aka asynchronous development).
Being capable of handling clothing decisions like a 9 or 10 yr old, but maybe deep down feeling more like 'can someone just please pick this stuff out, and take care of me, I'm only 5!' can probably be pretty frustrating...having stuff just show up in your room can really make you feel protected and taken care of, I'd think. It is odd to think this would cause any stress, but perhaps the idea of going off to school in a few weeks has intensified an unspoken need to feel protected (?)

Sorry to hear you are having a hard time explaining all this to a friend, I have tried a couple times speaking with a friend at work about ds9, who actually sounds pretty similar to her own dd10, but she is more 'old school' than me, being from another country. She thinks her own daughter is lazy when she doesn't show enthusiasm for her school work, not in need of further challenge (tested gt, in a pullout program so maybe she thinks that is sufficient). So even people with similar kids can have really different perspectives...