Several parents of non verbal kids, think this includes cerebral palsy, have posted on the message board over the years.
Try a message board search.
You might consider either a consult with one of the CVSA Medical Adviors (there is a list on the CVSA web page) or having your daughters daughter consult with a Medical Advisor. You might also email the CVSA office for the most up to date list of CVS specialists (firstname.lastname@example.org) in your area.
Blynda, message board moderator, has had the best luck with a neuro. Another parent has her chllld being seen by a neurogastroenterologist. Michael Gershon, PhD, MD, Columbia, ("The Enteric Nervous System: A Second Brain") was the first to link the Bran/Gut. Columbia is not terribly far from you, and maybe being seen there could be beneficial.
Lots of people do not get a prodrome. Some parents do note a pallor on the face, or pallor around the mouth, discoloration under the eyes, burps, acetone odor on the breath (I am told much of the population cannot detect this odor), impending or start of menstruation/hormonal changes, and other possible indicators of an impending episode.
Dr. V, adult CVSA Medical Advisor, has stated that the gastro track tends to run faster in those who have CVS but slows as a cycle approaches. This could be a sign for you as well.
Please stay in touch and let us know how things are going.