Brook was born and raised in Rochester, Kent, England. She is the daughter of Sandra, a cook, and Kenneth Parsons, a scaffolder. She has a younger brother, Damian, and an older half-sister, Sasha. Kenneth died aged 57 in Rochester from lung cancer on 26 November 2007, during Brook’s time on Strictly Come Dancing.
Brook attended The Thomas Aveling School in Warren Wood, Rochester. She then studied at the Italia Conti Academy of Theatre Arts in London for three years before becoming a professional model.