Initially unaware of the supernatural, she learned about werewolves and other monsters after almost being raped by her ex-lover. She was saved by Seth Pederson, (who was a werewolf at the time.) However, she saw him fully transformed and ran away in terror without bothering to thank him.
Luckily, she was able to properly thank him upon learning that not only did he go to the same school as her, but was also her brother as a result of an affair between his mother and Brooke's grandfather. Brooke was at first disgusted by the fact that she had a werewolf for a brother, but after a long talk with Emma Duvall, got over the petty hatred and accepted Seth as her brother.
By the start of Season 3, Brooke met Seth's girlfriend Erica, and over the course of several months, had an affair with her without Seth knowing about it. Feeling guilty, she ended the affair and told Seth, who was rightfully upset that his own sister was having sex with his girlfriend and never told him.
The gorgeous, sassy and wealthy Queen Bee of George Washignton High School, she is one of the best friends of Emma Duval. Initially, she is shown to be slightly snobby and shallow with a carefree attitude and blunt persona. However, as the series progresses, Brooke is revealed to be a troubled, insecure girl with family and daddy issues. Also, she had a complicated and secret sexual relationship with her teacher, Seth Branson. When her friends start to get picked off one by one by the Lakewood slasher, Brooke shows the most grief of her friends' deaths, revealing a more caring and sensitive side. Brooke is attacked on several occasions. In the first season finale, she is attacked while locked inside a freezer, suffering minor stab wounds but managed to survive. She is one of the Six Lakewood teens to survive the first Lakewood bloodbath. In the season 2 premiere, Brooke broke up with her abusive boyfriend Jake Fitzgerald, but was unaware that he was kidnapped, tortured, and murdered by the new Lakewood Slasher until much later when his body, blood and gore dropped all over her. She becomes angry and determined to find Jake's killer and avenge him, going as far as to torture Branson for information, but with no success. She slowly grows closer to Gustavo, especially when her father, Mayor Quinn Maddox, is murdered by the killer. While assisting Emma and the gang on setting up a trap for the killer, she is ambushed and stabbed by him in the Season 2 finale, but makes a quick recovery.
As he is the only sibling that Brooke knows about, he and Brooke are very close and protective of one another. This is proven when he saved Brooke from Mr. Branson, as well as when Brooke defended him from some bullies during a lunar eclipse, which rendered him powerless.
Despite not knowing much of anything about Erica, or even knowing what she was, she seemingly fell in love with her due to her sexy appearance, and began to secretly meet her at a motel almost every day for several months to have sex with her. Eventually, Brooke felt very guilty for what she was doing with her brother's girlfriend and admitted to him what she did. He was understandably hurt by the affair and didn't speak to Brooke for at least a year.