In that case:
--it's not too soon to evaluate. I'd look for a reputable neuropsych and look closely for writing disabilities and fine motor disabilities of all kinds.

--it is worth turning things around at school ASAP. The hit to self-esteem is real and can be lasting.

--I now see. I would absolutely scribe for her if she wants to write a book. Get her comfortable dictating work and putting sentences together, IF that is what she wants to do. Those are excellent writing skills. (Not pre-writing-- putting ideas into words is writing.)