Complex sentence: Her best friend, Cee-Saw, is constantly getting her into trouble but because of the events that happened in the book's prequel, Theresa's mother doubts her potential and expects her to fail.
Split into simpler sentences: Her best friend, Cee-Saw, constantly gets her into trouble. Because of the events that happened in the book's prequel, Theresa's mother doubts her potential and expects her to fail.