My fianc just got diagnosed with bilateral cerebellar tonsillar ectopia. our doctor did not say much, but im extremely worried and don't know what to?

Educate yourself.: Here is an article by the National Organization for Rare Disorders: https://rarediseases.org/rare-diseases/chiari-malformations/ Take care

The significance : Of that finding depends on the severity and any associated MRI abnormalities. If mild, and there are no other findings, it is likely an incidental finding of no clinical importance. This is called a Chiari 1 malformation. It can sometimes cause symptoms, however, so your doc needs to correlate.