Mandy is a shy, unpopular student at Neptune High. She refrains from standing up for herself, thus becoming a target of bullying, specifically by one student, Lenny Sofer, who found out she had a crush on him and been mean to her ever since.
Her best friend is her dog, Chester, a Jack Russell terrier. When Chester goes missing while she is babysitting for an 09er family, she puts up fliers around school but with less luck than ridicule by her schoolmates. When she asks for Veronica's help, Veronica is dubious as dogs aren't her specialty but decides to help her because she felt sorry for her.
Veronica uncovers a group stealing dogs from high income neighborhoods and only returning the ones whose owners pay high rewards, selling the dogs of those who could not. Mandy accompanies Veronica, Wallace, and Deputy Leo to the Pound when they unravel the plot. Mandy begins to leave in sorrow but encounters and attacks Hans, an accomplice who works at the pound, with a Stun Gun in rage when led to believe they had killed Chester, but found out that he was alive and found him in another home.
She reappears again, supporting Corny when he nominates Veronica as candidate for Homecoming Queen, happily telling everyone how Veronica had helped her find her dog.