Among the observers: her estranged husband Seal, from whom she split in January after the two were married for seven years. She filed for divorce in April.
"That's what happens when two people separate, they move on and generally meet other people in their lives," Seal, 49, told TMZ as he arrived at Los Angeles International Airport.
"I certainly don't expect Heidi to all of a sudden become a nun. But as always my main priority is the emotional well-being of my children, and to be quite honest if there is going to be someone else there in their lives there, I would much rather it was a familiar face," the singer said.
Also on the Sardinian vacation with the Project Runway host, 39, were her parents and her children: Leni, 8, Henry, 6½, Johan, 5½, and Lou, 2½.
Added Seal: "That's the only thing I would have preferred. Whilst I didn't expect anything better from him [the bodyguard], I would of thought that Heidi would have shown a little more class and at least waited until we separated first before deciding to fornicate with the help, as it were."
Saturday morning, Klum was seen having breakfast in Beverly Hills. She has not commented on any relationship.