The actress is lucky enough to live next to the Chanel designer in Paris and the pair have formed a solid friendship based on their mutual love of their furry feline friends.
Karl is so besotted with his pet cat Choupette that he famously pays for two maids to wait on her every need around the clock, lets her dine at his table, and has set the white Siamese up with her own iPad and Twitter account.
Diane told Stylist magazine: ''I run into him a lot, especially as he prefers to work at night. I'll come home late and he's often in the street shooting, then he'll invite me up for dinner or a glass of wine and a chat. It's lovely to have him right next door.
''We do share a passion for cats ... I also have a cat - not quite as well-groomed and pretty as his, I might add - so we exchange cat pictures, which I guess is a bit sad, but also really great.''
Despite the 37-year-old actress' pet not leading the same pampered lifestyle as Choupette, the 'A Perfect Plan' star claims her cat is just as well-travelled.
She added: ''He's here in LA. But he comes places with me, he travels. He doesn't have a passport but he loves being in the car. He's a total travelling cat.''
German-born Diane feels most at home in Paris, but enjoys the constant sunshine in Los Angeles because it helps her hobby of growing her own organic vegetables.
She said: ''LA isn't your typical American city, everybody here seems to be on some crazy health kick, living on juices. Although I don't subscribe to any of that, I do love the way that everything grows here all year round.
''I've just started a vegetable garden at home; it's been amazing to be able to go to my own garden, pick my own kale and make my own kale chips.''
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