Kelnot,

Welcome to NeuroTalk. I bet your sister has suffered many concussions. She just worked past/through them. Plus, many sub -concussive impacts.

Has she been assessed by a Vestibular Rehabilitation Therapist ? Sounds like it may help. She also may have a subtle upper neck injury that needs careful treatment.

Undiagnosed PCS will not develop into something worse unless her dizziness causes her to fall and injure herself.