Rebel Wilson Wears Custom Givenchy Couture Dress, Says It's a 'Cool Move' for Size-Inclusive Style

Rebel Wilson is living a true life fashion fairytale.

The actress attended the annual InStyle Awards on Monday night to award Elizabeth Stewart the Stylist of the Year honor. But Wilson didn’t choose just any black tie outfit — she wore a black lace Givenchy Couture dress made especially for her.

“I think the last big couture piece that [Givenchy artistic director] Clare Waight Keller did was Meghan Markle‘s wedding dress,” Wilson tells PEOPLE exclusively. “And now she’s making me a dress so that’s kind of amazing just in and of itself. But then factor in the fact that it’s Givenchy – an amazing Paris fashion house — I’m a bit shocked how it all happened but really grateful. I think it’s a really cool move that they’re being inclusive with someone like me.”

In addition to designing Markle’s royal wedding gown, Givenchy is known for dressing Hollywood actresses including Cate Blanchett, Rosamund Pike and Julianne Moore.

“I could be wrong but Givenchy normally makes sample sizes, and obviously, I’m not sample size,” Wilson says. “I don’t know if they’ve ever made a plus-size couture dress before, they may have, but my stylist, Elizabeth Stewart, told me, ‘This is a massive deal.’ She’s never heard of them doing something like this.'”

To document Wilson’s high-fashion night, she shared a sneak peek of her dress exclusively with PEOPLE before she hit the carpet with some fun getting-ready snaps.

If you’re wondering how the dress-making process began, so is Wilson!

“I don’t quite know how it came about,” says Wilson, who met Keller for the first time on Sunday.

“I’m guessing that Clare has children who might have liked some of my movies? Because I don’t think [Givenchy] would look at me and think high-fashion. Givenchy is the number one ranking fashion house in the world right now so I am shocked and surprised.”

But once the brand was on board, Wilson relied on Stewart, whose other clients include Julia Roberts, Gal Gadot, Blanchett and Sandra Bullock, to make the look come alive.

“This is the first time Rebel and Clare have worked together,” Stewart tells PEOPLE. “We asked for a dress with the classic Audrey Hepburn vibe, and Clare sent the perfect sketch.”

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Wilson says that Keller’s black dress is both comfortable and flattering.

“That’s a really hard balance for someone who’s plus-size,” says Wilson, who accessorized with Givenchy heels, a blue clutch and Givenchy glasses, which came straight off the runway.

The look came together perfectly and just in the nick of time as Wilson only tried the dress on the day before the event.

“We had a backup dress ready to go just in case it didn’t fit,” she reveals, but quickly learned that that wasn’t necessary. “The crazy thing is, I tried it on yesterday and it was perfect.”

This marks a very significant step from a high-end couture label to celebrate more size-inclusive fashion.

“I’m the average size and the average height of an American woman,” says Wilson. “There’s so many more people who look like me than a fashion model so this is an awesome, positive move that Givenchy is doing by being inclusive of someone like me.”

Watch: Rebel Wilson and Laura Brown Show Off Matching ‘Rebel Wilson Angels’ Jackets

“I do hope this inspires more fashion houses to create looks for all sizes,” adds Stewart. “There is already a head start, my good friend Patrick Herning started a website called 11Honore that collaborates with high-end designers for inclusive sizing.”

So if she gets to keep the creation, will we see her rocking her Givenchy dress again on the red carpet? “Oh yeah, it’s the perfect classy black tie dress,” she says enthusiastically.