The first thing we learn about Jenny Wren is that she was born with underdeveloped legs and a crooked spine. But in spite of her disadvantage, she thinks of herself as being no different from any other teenage girl. For example, she often thinks about her future husband, and takes pride in the thought that he'll bow down before her like a servant.
As we learn from the book,
Jenny Wren had her personal vanities—happily for her—and no intentions were stronger in her breast than the various trials and torments that were, in the fullness of time, to be inflicted upon "him." (6.2.12)
Now you could say that Jenny Wren is completely delusional if she thinks any man will be her love slave. But you might also consider her brave for choosing to live with pride in spite of her spine and legs.
Jenny Wren plans on treating her future husband like a slave are totally consistent with the fact that she already treats her father like a child. Not only does she treat her (no good, drunken) daddy like a kid, she refers to him as one. She says to Lizzie at one point, "And my child is a troublesome and bad child, and costs me a world of scolding" (6.2.79)… and she's talking about her father.
In fact, Jenny treats nearly every adult man in her life as a child, and in this, we can see evidence of the fact that she's compensating for her physical appearance by taking on a position of authority over every man she meets.
She even likes to talk about rejecting men who have no romantic interest in her to begin with, as she tells Lizzie, "Why the last news is, that I don't mean to marry your brother" (6.2.4). In spite of her weirdo behavior and tendency to infantilize men, though, Jenny is a good person with a good heart, and there's no doubt that Dickens wants us to sympathize with her.