'Life & Style' has learned that Mariah Carey was 45 minutes late to a recent manicure appointment at the Beverly Wilshire hotel—because she was catching up on some beauty sleep in her car!

“Her two assistants came in to inform the staff that Mariah wasn’t ready to get out of the car,” a source exclusively tells 'Life & Style.'

“They said Mariah was sleeping and that she does not like to be woken up—ever! They said she likes to wake up naturally, ‘so you’ll have to wait.’”

How was Mariah feeling after her nap? “She was surprisingly nice,” adds the insider. “We were relieved she wasn’t a nightmare!”

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