Although I also prefer that the primary disability be identified, the law does not require that services be limited to those typically associated with the named disability. As long as she has a qualifying disability, services and accommodations should be based on needs. It sounds like the 504 allows for typing (you might see if you can get spellcheck in it). What more of substance would you anticipate from a dysgraphia label than what you already have?

...pronounced like the long vowel and first letter of the alphabet...