Some symptoms of PTSD are:
- Re-experiencing the trauma through intrusive distressing recollections of the event, flashbacks, and nightmares.
- Emotional numbness and avoidance of places, people, and activities that are reminders of the trauma.
- Being easily irritated or angered
PTSD relates to the life Vola is living because Peter found Vola living on a farm...in the middle of nowhere! She even admits it herself. This relates the symptom 2, but instead of avoiding things that remind her of the "experience", she seems to be avoiding all civilization. Symptom 1 is related to Vola too. When Peter did the show for Vola, he changed it last moment and changed it to Vola's life in the war. This made her remember the event, causing her to re-experience the trauma. Of course, Peter didn't mean for this to happen. And finally, I think Vola's life is related to symptom 3 because in the story, Vola got angry right away when she found out Peter took her knife.