No answers here, but your DD sounds exactly like my DS7 in the ways you mention. He loves to draw (even draws with 3D perspective), but is very slow (but extremely neat) in the writing department. It's hard to say at his age whether he has an LD or this is just an area of relative weakness for him that will develop at a different pace. So we've adopted a wait-and-see approach but it's on our radar, for sure.
It's easy think that relative weaknesses in gifted kids, when compared with what they can do, can seem really glaring, yet when compared to more typical kids is right about average.
How is her fluency with arithmetic? DS has high math reasoning ability yet average (even slightly below average) fluency. This has a tendency to mask what he think about in math, since so much at this age is geared towards fluency.
For what it's worth, I don't believe that dysgraphia has anything to do with fine motor skills. It's more related to dyslexia.
