Hi and welcome to the Chiari forum.
In order to answer your questions I feel I need to ask a few....like what surgery did she have? There are different types of Posterior fossa decompression surgeries, one does NOT open the dura, the other one DOES.
Next, were ALL related conditions ruled out? The reason I ask is because if the dura was opened and a patch placed and she has Ehlers-Danlos, depending on what patch they used could be causing her issues?
What has her Dr said at follow up visits?