Kristina Frye is a mentalist as Patrick Jane . She is so damn clever . she some times solves things before Patrick Jane does . And when the scene happened that Red John kidnapped her . she took her passport with her and her stuff . Red john didn't kill her because she is Red John . when she decided to come back and show her self , she claims that she was hypnotized to believe that she is dead so that Jane doesn't suspect her . And If you rewatched S2 E22 and E23 and the day that she return you will find out her actions . She shook hands with Patrick Jane and they we're not friends . remember when Jane went to the bathroom :) . He was gonna tell her some thing that he can't stay with her , but he got a call for the office .