Hi Sophiesmom and welcome to NeuroTalk. I admit to being unable to find a forum here for Dandy-Walker w/Orthostatic Headaches so am unable to direct you anywhere. I'm so sorry for your daughters condition.
You might try posting this in our Rare Disorders Forum and see if you get any responses.
Here is that link...
http://neurotalk.psychcentral.com/forum2.html
These forums are wonderful for exchanging information and finding support.