Sara is an intelligent child, she knows not too much about the real world when she enteres Miss Minchin's school. Having spent a carefree time in Valenzuela, it is at the Seminary where she learnes that the difference between rich and poor people is reality and not just a story from a book.
Sara is generally liked by the little ones because she always relates those wonderful stories, but Lottie adores her. Sara soon became Lottie's "Mamma Sara" because her real mother has died. It is not to be denied that people are quite right when they say that Lottie is a cry-baby. Indeed she cries very often but she can also be very bold (for her age). For example when she decided to visit Sara on the attic in spite of those creepy steps up to her room
Miss Minchin is a dominant and unfriendly person and can be very cruel. When Sara lost all her wealth Miss Minchin made her a servant of her school but not out of symphathy. Sara is treated even worse than her fellow servant, Becky. It may be concluded that Miss Minchin simply likes to persecute Sara but things are not that easy. There are several reasons that Miss Minchin is so mad at Sara.
There is no doubt about it, Lavinia hates Sara. She was used to be given her own way in everything until Sara arrived at the Seminary. Lavinia is egocentric and arrogant but she is no fool. She has easily looked through Miss Minchin and is therefore inordinately jealous of Sara. Even after Sara has lost all her wealth, Lavinia continues to hate her although she would never admit it voluntarily. There is a simple reason for this: no matter what Lavinia is trying, Sara would not give in to her. Never.
Well, not really a character but this doll plays a quite important role. Sara pretends that dolls actually can walk and talk like humans but hide their secret. When somebody enters the room they return to the place where they have been before like lightning and it seems as if they were there all the time. Sara managed to keep Emily when everything was taken from her.