The Balmain creative director recently collaborated with the lip kit guru on a capsule cosmetics collection and named the Keeping Up With the Kardashians star artistic director of make-up for his spring 2020 show - which she ultimately missed due to illness - and he has praised his pal as a "strong" and confident woman who wants her friends to "feel good".
He said: "She's such a strong woman and I love the way that she's so confident and always making sure that her friends are feeling good. And she's so generous.
"When you do have problems, she will always be there for you. It's a beautiful relationship."
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Olivier thinks fashion is currently a "bit boring" and he wants designers to up their game.
He told the Hollywood Reporter: "That last show was a celebration of beauty and joy at a moment of fashion which is a bit boring. I feel like we need to step it up...
"When it's about my fashion shows, I want to make sure that people enjoy them and have a bit of light in their life."
The French designer loves spending time in New York because of the city's "energy".
He said: "For me, New York is just [about] walking around the streets, because they have such a great energy. And I love spending time with my friends in the house and watching movies all night. I'm not really a party boy...
"[My visits to New York] are not often enough, and then only for a day or two.
"I am always in L.A. Again, I don't stay long, but I have a lot of friends there."