A source said: "After a big fight with him, Cameron noticed a grey hair she hadn't seen before. She joked that she named it 'Paul' because he was probably the reason she had it."

Among the topics the couple are believed to argue about is 38-year-old Paul's lack of commitment.

The source added to the National Enquirer magazine: "She thought she'd have an engagement ring by now, but Paul's dragging his feet. It's stressing her out."

Earlier this year, Cameron was spotted carrying a photograph of British supermodel Kate Moss into a Beverly Hills hair salon and asking her stylist to copy Kate's look.

A source said: "Cameron is obviously a fan of Kate's hair. She took the photograph with her and showed the stylist exactly what she wanted