Hi my son has same problems, he has daily exersice plan, it varies, simply he stands with hands on wall pushing them, uses weights on each hand, theraputty,he has a blown up peanut he puts his stomach on and rolls hands on floor. The occupational therapist also advised us to let him carry heavy loads, bags etc,the more these are done in a day the better. We do 10 minutes at school before he goes to class. I have actually witnessed how his handwritting is improved. Good luck i hope this helps your daughter.
I really appreciated reading that sensory processing deficits can be inconsistent; meaning, present one day and not the next. That is absolutely my experience