Character Analysis
Theresa's the rough-and-tumble one in the gang. She has "black curly hair that's flat on one side, as if she slept on it. She's missing half of her teeth" (2.48). She's pretty headstrong, too, the type to demand something rather than ask for it, and make her own decisions no matter what: "Theresa pays no attention. The tower might as well be a tree for all she cares" (3.2). Yup, girl is doing her own thing, no two ways about it.
But this doesn't mean Theresa's selfish—unlike Piper, this headstrong young lady also has a big heart. When all the kids get called into the warden's office except for her, she volunteers to come along, no questions asked, saying: "'I have to come. Who's going to get you out of trouble?'" (19.26). Another great example is in how attentive she is to her baby brother. When Piper tells Theresa not to bring the baby on one of their schemes, "Theresa must have decided that if Rocky can't come, she's not going either. It's almost as if she gave birth to that baby herself" (22.4). Nobody puts Theresa's baby brother in the corner.
Rocky isn't the only person that Theresa dotes on with a mother's love, though; she also has a knack for understanding Natalie. This shows Theresa's attentive side. She always seems to know how to distract or entertain Natalie: "Theresa has a real instinct for what Natalie will find fascinating" (36.11). Sure, it might be partially instinct, but another part is definitely simply taking the time to pay attention and understand Natalie—something many other characters barely bother doing.