This is Tiffany, walking back home. Start with the boots. They are big and heavy boots, much repaired by her father, and they belonged to various sisters before her; she wears several pairs of socks to keep them on. They are big. Tiffany sometimes feels she is nothing more than a way of moving boots around. (1.42)
At the very beginning, it's hard for Tiffany to have a true sense of herself because she's seen as such a part of the Aching clan. She's just another Aching girl, not an actual individual.
People tended to leave Tiffany alone. There was nothing particularly cruel or unpleasant about this, but the farm was big and everyone had their jobs to do, and she did hers very well and so she became, in a way, invisible. (1.58)
The farm is so big and there are so many sisters around that Tiffany really doesn't get much attention at the beginning of the story. Her parents don't pay that much attention to her at all—especially when Wentworth comes around.
"It's all a bit… foggy. I just know I've been a person. At least, I think I know. It gives me the willies. Sometimes I wake up in the night and I think, was I ever really human? Or was I just a toad that got on her nerves and she made me think I was human once?" (4.22)
That poor toad. He has no idea who or what he is at all, and doesn't even know for sure if he was once a human. That's got to mess with a little amphibian's head (and personal identity).
"Yes," said a voice and Tiffany realized that it was hers again. The anger rose up, joyfully. "Yes! I'm me! I am careful and logical and I look up things I don't understand! When I hear people use the wrong words, I get edgy! I am good with cheese. I read books fast! I think! And I always have a piece of string! That's the kind of person I am!" (12.97)
What an epiphany—the Queen may have said all these nasty things about Tiffany, but she knows that she's got lots of skills and qualities that make her an interesting and strong person.
"What a shame," said the Queen. "You've let everybody down, haven't you?" (12.222)
The Queen tries to chip away at Tiffany's confidence by telling her that she's let everyone down and that she's a bad person. That's a cheap shot and rather hypocritical, don't you think?
"You dreamed you could invade my world with a frying pan. You had this dream about Brave Girl Rescuing Little Brother. You thought you were the heroine of a story." (13.4)
Talk about a mean taunting. The Queen definitely knows how to hit Tiffany where it hurts, and make her reconsider if what she did was right after all.
She saw the smile in the Queen's eyes, and thought: Which one of all those people doing all that thinking is me?
Is there really any me at all? (13.22-23)
When the Queen continues to insinuate that Tiffany failed everyone, her confidence starts to falter as she begins to wonder if she really is worthwhile and if she's done anything right at all.
But Tiffany's Third Thoughts said: Then turn selfishness into a weapon! Make all things yours! Make other lives and dreams and hopes yours! Protect them! Save them! Bring them into the sheep fold! (13.64)
Thankfully Tiffany has her Third Thoughts to save her, which tell her that she can use her bad qualities—like selfishness—for good. She can turn them around and use them to save other people.
The wheels of stars and years, of space and time, locked into place. She knew exactly where she was, and who she was, and what she was. (13.148)
Once Grandma Aching comes around, Tiffany is again grounded with the knowledge that she's a true Aching woman too. She knows who she is and how she has to fight back. And that's exactly what she does.
So… Roland with the beefy face was the hero, was he? And she was just like the stupid princess who broke her ankle and fainted all the time. That was completely unfair! (14.173)
Ugh. How annoying. Even though Tiffany's the one who saved the day, Roland is taking all the credit. Oh well, she knows that she did it where it really counts—plus, as a witch, it's not her job to take the credit at all.