Harcourt was in a "massive queue" at LAX when "my phone just started going mad" with calls from friends telling her about Kidman's name drop.
"Honestly I do not know how she's managed to be such a perfect human being with the insane lifestyle she must lead," muses Harcourt.
The Kiwi acting coach was the one who coached Kidman in her first stage role in 17 years in 2015 - Photograph 51 on London's West End, which Kidman wound up winning best actress at the West End Theatre Awards for.
Since then, Harcourt has been Kidman's go-to on projects including The Killing of a Sacred Deer, The Beguiled and her hit series Big Little Lies, for which she won her Emmy on Monday.
"We've got a great relationship, she's a no-bullshit person, she's very Australian. She's extremely smart...she's very intuitive and she just needs someone else who's a no-bullshit person and who can work fast, efficiently and any time of the day or night.
"She's really busy so it's really useful for her to have a sounding board or someone she can just bounce ideas around with."
And while she says it's not the first time Kidman and other clients have thanked her on such a public stage, it does still take some getting used to.
"It makes me laugh to be the random Kiwi chick down here at the bottom of the world working with these big Hollywood stars, but it's fun. It's really fun for me."
Harcourt's latest project is Kiwi film The Changeover which stars UK actor Timothy Spall and New Zealand's own Melanie Lynskey, who Harcourt has been working with for nearly 25 years since working on Lynskey's first film, Heavenly Creatures.
The Changeover, based on Margaret Mahy's book of the same name, opens in cinemas around New Zealand on September 28.