Jean Brodie is subject to a lot of this. She says that she opted to stay away from Teddy Lloyd to devote her life to teaching young girls. But Sandy especially calls her out that she selects certain girls that merely appeal to her vanity and seem easy to manipulate. There's also the question of whether Jean picks girls for the "Brodie set" because they remind her of herself (Jenny in particular) or because she feels affection for them. There's also the possibility that the Brodie set she views as the children she never had.
The Love Triangle between Teddy Lloyd and Gordon Lowther. Jean could either enjoy stringing both of them along and simply not want to have to pick one. Or she could be keeping Lowther at bay because she doesn't love him and doesn't want to trap him in an unhappy marriage with her when she still pines for Lloyd. Or she could have been intending to marry Lowther once Jenny had started her affair, in effect having both men at last.
Miss Mackay's attempts to dismiss Jean Brodie. It's either her not wanting such a radical teacher at Marcia Blaine or a personal vendetta against a teacher that's been very hard to get rid of. Miss Mackay's eventual reasons for succeeding support the former, but she definitely seems a little too pleased when she does.
Sandy's reasons for betraying Jean Brodie are either motivated by a desire to protect the rest of the girls (and preventing another death) or jealousy that Teddy Lloyd still painted Jean whenever she posed for him. The film also shows her crying at the end, which suggests that she's going My God, What Have I Done? alongside I Did What I Had to Do.
Tear Jerker: Mary McGregor and her ultimate fate. She's an orphan who gets bullied by the other girls, even those in the "Brodie Set". And she takes the terrible advice of the one mother figure she's ever known - and runs off to join the army. Her train gets bombed before she even gets there - and it turns out that she was headed for the wrong army. She had intended to join her brother, assuming he was fighting for Franco when he was fighting for the Republic. So not only did she die for nothing, she never got reunited with her brother and if she'd headed to the other side - she might at least have lived long enough.
The Woobie: Poor, slow Mary McGregor who has no one except a delinquent brother and Miss Brodie.
Mr Lowther, a decent, guileless sort who is strung along by Miss Brodie for years.