We too have a kiddo with a dysgraphia dx. For her, the major clues were delayed gross motor skills (the original dx was dyspraxia), timed parts of the WISC were average (truly spot on average compared to 98th-99.9th in many/most of the other parts of the WISC), and consistent worse performance on timed or fluency measures. She's the one I was mentioning earlier with the WJ scores.
She is one, however, who was much more easily recognized as gifted than my other 2e kiddo b/c, while slower with output, her depth of thinking & writing content as well as reading comprehension were really obvious to teachers. For instance, when other first graders were reading Henry & Mudge, she was reading Harry Potter &, unlike your dd, she was one who would give detailed in depth responses when asked to tell about what she'd read. One other example that comes to mind was a poem they were asked to write in elementary school which started with the prompt "I am [two things that describe you]." A lot of the kids' poems started with stuff like "I am tall and blond." Dd's started as "I am a slave to the desert but my heart belongs to the sea."
I totally get how much harder it is to get accommodations for gifted kids who don't "out" themselves so obviously, though. My youngest is more like your dd and it was really hard in the early yrs.
