She reads his diary

I borrowed a book in the library. It was Portret van een jongeman by Coetzee. I am really keen on reading this author once again. I read the very first page in Dutch, I understood. So I brought home and  read twenty pages with pain and dictionary. The boy brings back his girlfriend at home and she decides to stay days. He writes what he feels in his diary and she reads it. She gets angry. Can she be?