"The younger one is the quiet, shy one and my older, Lily-Grace, is the more outgoing, loud sister," Nicky Hilton told PEOPLE Wednesday

By Jen Juneau and Mariah Haas
April 19, 2018 11:45 AM

Look out — there’s a new pair of Hilton sisters about to take the world by storm.

PEOPLE caught up with Nicky Hilton Rothschild Wednesday at the CASA of Los Angeles’ 2018 Evening to Foster Dreams Gala, where the heiress dished on the difference between her two daughters: Theodora “Teddy” Marilyn, 4 months on Friday, and Lily-Grace Victoria, 21 months.

“It’s very interesting. You definitely see the difference,” said Hilton Rothschild, 34, who attended the gala event alongside sister Paris Hilton. “There’s a Paris and a Nicky. The younger one is the quiet, shy one and my older, Lily-Grace, is the more outgoing, loud sister.”

The mom of two added that although her daughters are still very young, it’s fun to be “watching them grow every single day” and “you can see their personalities already at this age.”

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The Colleagues And Oscar de la Renta's Annual Spring Luncheon
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Hilton Rothschild — who lives with her children and husband James Rothschild in a stunning New York City penthouse — told PEOPLE it was “very important” for her to be on hand for Wednesday night’s gala.

But she had to be creative about flying to the west coast. “I literally took the last flight out of New York, and I’m leaving right after this event to get back home to them,” she says.

CASA Of Los Angeles' 2018 Evening To Foster Dreams Gala - Red Carpet
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Credit: Nicky Hilton/Instagram

RELATED VIDEO: Nicky Hilton Rothschild Welcomes Daughter Teddy Marilyn

Hilton Rothschild says while her younger daughter is “too teeny” to participate in Aunt Paris’ upcoming wedding ceremony, Lily-Grace will definitely be a flower girl.

But is the fashion designer planning to help make Lily-Grace’s dress? “No,” Hilton Rothschild says with a laugh. “[I’m going to] buy one.”