Actions certainly speak louder than words, especially in this story. Sara continually proves herself to be a much better person than Miss Minchin and Lavinia by keeping her chin up and not giving into their nasty games. She doesn't slap Lavinia (even though she wants to) and continues to act respectably even when she's hungry and freezing.
Instead of just talking about acting like a princess, she puts her money where her mouth is (or something) and gives five of her six buns to a poor beggar child, even when she herself is so hungry she could eat a whole moose.
Actions also give us a little insight into what a truly terrible person Miss Minchin is. At the beginning, she acts like she adores Sara, but we know that it's all lies as soon as Sara's lost her money. She shows no compassion and instead takes pleasure in making a newly orphaned girl more miserable than she has to be. What an adult thing to do!
She also tries to convince Mr. Carrisford and Sara that she always meant well at the end, but her words have no effect. Her actions this whole time have shown her to be a mean, greedy, uncompassionate woman--and no one's fooled.
It's kind of a weird thing to get hung up on, but take a look around and think about how important clothes are to everyone around you. Is he wearing Toms or Vans? Does she wear shorts or skirts? Does she buy exclusively designer clothes or shop at Tar-zhay? What you wear says stuff about you—even if what it says is that you don't care—and the characters in A Little Princess know that.
At the beginning, Sara gets to stand at the head of the line because she has sumptuous clothes, bought by her adoring father. When she experiences her fall from grace, though, she dresses in old clothes and rags and people don't see her as a fine lady or princess anymore. Instead, everyone thinks she's just a maid or beggar. Even Mr. Carrisford is fooled and doesn't recognize her for his friend's daughter because she's so shabbily dressed.
Speech and Dialogue
We learn a lot about the different characters from their speech. For example, Miss Minchin is extraordinarily cold in her speech: You will have no time for dolls in future," she says: "You will have to work and improve yourself and make yourself useful" (7.1). Gee, Miss Minchin. That's awfully compassionate of you to say to a little girl whose entire world has just been turned upside down.
But it's not just what people say—it's how they say it. Check out how Sara responds to Guy Clarence from the Large Family, when he gives her a sixpence: "Thank you," she said. "You are a kind, kind little darling thing" (10.14).
Sara's refined speech tells the Large Family (and the reader) that she's more than just a little beggar girl. She's a little princess at heart, and she always will be.
In contrast, Becky is never going to be anything but a servant. When Sara catches her sleeping in her favorite chair, she says "Ain't—ain't yer angry, miss? … Ain't yer goin' to tell the missus?" (5.1). Just as Sara is a little princess no matter what she's wearing, Becky is a poor little servant girl, even after the Magic begins to fatten her up.
(Think all this accent stuff is funny? It used to be really important in England. Hey, they made a whole musical about it.
Thoughts and Opinions
Oh, boy. If there's one thing we could say about having an omniscient narrator, it's that we never ever stop hearing about what everyone thinks of each other. For example, Lavinia thinks Sara is weird and that she puts on airs; Miss Minchin thinks that Sara is spoiled and way too independent-minded for her taste; Becky thinks Sara is absolutely amazing and wonderful; and Ermengarde thinks that everyone thinks she's stupid and fat. (She's wrong: only some people think she's stupid and fat.)
Sara thinks a lot of things too, and she's certainly not afraid to express them. When Miss Minchin asks her to thank her after her father has died, Sara scoffs: "You are not kind," she said. "You are not kind, and it is not a home" (7.188).
Looks like her opinion of Miss Minchin is crystal clear.