First off, to put it out there, Miss Bianca is a very special mouse, physically and socially.
She has ermine white fur, which is unusual, and something even more special is that she has big brown eyes, while other white mice have pink or black eyes.
I am surprised that she is not snotty and self-entitled: instead, Miss Bianca is a polite little lady, and very empathetic. Most people or mice, after living in a fancy pagoda (especially the Porcelain Pagoda) without any worries except to help their master with his arithmetic problems (the boy), would get at least a little bit spoiled! Miss Bianca though, is as deferential and courteous than the other mice, and definitely even more!
Even so, shifting from the Porcelain Pagoda to the Mouse Prisoners’ Aid Society is tremendous. It’s similar to royalty mixing with common people, from riches to rags. However, Miss Bianca handled this change a lot better than a queen would handle it. I can just imagine the queen staring in disbelief at the servants mooching around the unwashed dishes in the sink and throwing a furious tantrum.
After reading the beginning of The Turret, I think that this point in life is probably very confusing and crushing for Miss Bianca.
First, she didn’t really want to resign, so she was hesitant to sign the resignation letter, but after thinking about helping the boy and writing her volume of poetry, she decided that she was obligated to stay in private life. Following this, at her retirement party she discovers someone who is being held prisoner in the old turret. Because of her nature, of course Miss Bianca wants to rescue this prisoner. After that, she realizes that this prisoner is Mandrake, an evil man who was cruel and pitiless to the poor Patience, so Miss Bianca is conflicted about whether to rescue him or not. Finally, she decides that it is her duty to rescue prisoners, even if they are vile, even though she knows that Mandrake was “completely odious.” So she announces it to the Society, but everybody hates Mandrake, so not a single mouse wants to rescue him and some hissed at Miss Bianca. This probably humiliated her and damaged her ego, because there is no doubt that she had never had this type of social problem in her life.
Miss Bianca might also be annoyed at Bernard. They have been great friends with each other for a length of time already, but when Miss Bianca wants to rescue a prisoner, Bernard turns his back on her, leaving her to do everything by herself.
She is getting her character tested differently now, in working alone. In the first two books, she had to be brave, quick, and cunning, working with other mice to rescue the prisoners. Now, she hasn’t gotten to rescue the prisoner, but is trying to be able to rescue him. Miss Bianca has already gotten put down horribly. Her determination to rescue is tested, and so is her inner strength. Also her independence. Miss Bianca must think to herself: Well, since they won’t help me, then I won’t use their help. I can do this!
And as we all know, she can.