The singer took dancer Derek Hough to a dinner party held for Piers and new wife Celia on the terrace of the Beverly Wilshire hotel in the Hollywood Hills on Saturday night .
'You're alive!' Piers joked as Cheryl made her entrance in a shimmering blue dress, showing off her new hair extensions.
Still on the mend from malaria, she declined a drink at first, before changing her mind.
'I'm not supposed to,' Cheryl, 27, told Piers, 45, who writes about the evening in his Inside column in The Mail On Sunday.
'Well, I suppose a small apple martini isn't going to kill me.'
Piers tried to feed Cheryl a caviar canapé but she didn't fancy snacking on fish eggs.
'I hate the stuff!' she told him. 'I'll have a fag instead.'
Cheryl then partied with Piers' pals Amanda Holden and Sharon Osbourne until the early hours.