The 34-year-old glamour model has allegedly started a hidden romance with former soccer ace David Beckham's best friend.
The couple were recently spotted separately leaving a party at a London nightclub, reported Contactmusic.
"Kelly and Dave are smitten. When Kelly was in LA recently auditioning for the 'Entourage' movie he flew out. They've been talking on the phone daily," a source said.
Brook and Gardner were first spotted together at a club in September after she split from her ex-boyfriend Danny Cipriani.