Incorrectly Regarded as Mistake: attorney-client privilege does not apply in circumstances where no legal advice was sought (all Dean asked for was information about a woman's death and where she was buried, not his court case) or in conversations where information aided/abetted a criminal act. Both are true for Dean and Mara's conversation, therefore she has to tell Henriksen and does not have privilege.
Canadians obviously don't understand the American justice system. Any attorney who divulges their client's statements is subject to being disbarred and sued by their client. Regardless of circumstances.