The Prime of Miss Jean Brodie

I thought that ending of the book was rather interesting. Sandy, the girl that Jean Brodie thought she could trust the most, "betrayed" her by telling Miss. Mackay that she taught and encouraged Facism to her students. Of course Miss. Mackay opened Sandy's explanation with open arms. Miss. Brodie was convinced that it couldn't be Sandy that betrayed her. Sandy stated, "It's only possible to betray where loyalty is due". (Pg. 136) Sandy only believed she owed Miss Brodie loyalty to a certain extent. Did Sandy do this because of Mr. Lloyd's fascination with Jean Brodie? Or was it because Sandy was annoyed after all these years of Miss. Brodie's 'manipulation' and 'opinions'? Another point that I found interesting was that Miss. Brodie ended up going down for being "Facist"after all. All along she was freely teaching on a personal level and pressing her beliefs upon the students. I guess it burned her in the end. Then again, that opens another whole place for discussion.