So, what do you think Miss Minchin's problem with Sarah was?

I always wondered if Ms Minchin maybe knew Sara's mother and they had a falling out of some sort. She keeps taking the locket with Sara's parents' pictures in it. I wonder if she is taking out her feelings from the past out on Sara, along with the jealousy/fear she feels for Sara herself. Maybe Sara's mom was a lot like Sara and so Ms Minchin is frustrated that she has to go through it all again. It brings back bitter memories. Like Harry did for Snape, just not for the same reasons. If that at all makes sense.

Jealousy and resentment.

The book and the film approach Miss Minchin's disdain towards Sara in different ways. In the novel, it is clear that Miss Minchin is the sort of woman to keep up appearances but run a tight ship. She frequently loses her temper, but at the same time manages to come across as a caring overseer when parents come calling. When Sara receives the dreadful news of her father's death and her penniless state, Miss Minchin is almost startled that she carries herself with the same sense of self-worth that she did when she was wealthy. This strong will is exasperating, as Miss Minchin is the sort of character to desire control. She cannot control Sara's ability to overcome her situation.

The movie's approach is a bit different. Like book Minchin, movie Minchin also runs a tight ship. However, it is also clear that the Minchin family dynamic is strained. Though Amelia is the co-proprietor of the seminary, she is completely subservient to her sister. Unlike the book, where Maria and Amelia communicate several times throughout, they barely speak to each other in the movie unless Miss Minchin is giving Amelia an order.

Also, I think it's clear after Sara has her big, defiant "all girls are princesses" speech that she has hit a nerve. Perhaps Mr. Minchin was a no-nonsense realist and instilled in Miss Minchin a similar world view. Maybe he was a cruel man who showed no love or concern for his daughters. It really presents an interesting series of questions as Amelia was raised in the same household, but unlike Miss Minchin, Amelia is gentle and kind. Perhaps these questions are never answered, but it does add a compelling layer to the character of the antagonist.

In a nutshell; jealousy and insecurity. Her father obviously told her once that she was a princess as well. Sarah represents the girl she no longer is and she misses how she used to be. She is old enough that it is also obvious that her father is gone also. She identifies with Sarah and is jealous to see her with such a kind father.

Duality between the hero and villain is very common in storytelling. Both characters are united ironically with one trait. Both miss their fathers who cared for them. However, they respond with very different actions. One chooses to be selfless and help others and the other looks inward to please them-self at the expense of others.

Good movie. Excellent villain.

I definitely think it was jealousy about Sara's wealth, upbringing and education (she did not like being shown up/embarrassed) in the french scene. I think its then compounded by the fact that she was obviously never shown even a fraction of the love that Sara was shown by her father. I dont think shes an altogether bad person, I mean she did continue to provide Sara shelter when she could have kicked her out. this may have been just to rub it in her face all the time but regardless it was far better than the alternative

It was easier to understand in the Shirley Temple film than in this one. In that one, Miss Minchin liked people with money, and was very kind to Sarah....when she was wealthy. The moment her dad died and left her without a penny, the headmistress's attitude changed faster than flipping a coin, particularly since the child had nowhere to go, and was now a burden.

I think one reason she didn't like Sarah in this film, was because Sarah was smarter and more independent than the other girls. That, and even when she was poor, Sarah could still influence people, and it scared the living daylights out of her. Minchin feared losing her power over the other girls, no thanks to Sarah teaching them to think outside the box.