The model replaced her mother Christie Brinkley on season 28 of Dancing with the Stars

Sailor Brinkley-Cook has her eyes on the mirrorball trophy!

The Sports Illustrated model, who is filling in for her mom Christie Brinkley after she fell and broke her arm ahead of Monday’s Dancing with the Stars premiere, gave fans a sneak peek into her intense studio rehearsals on her Instagram Stories this week.

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In between practicing her rumba routine with pro partner Val Chmerkovskiy, Sailor, 21, made sure to document all their fun and excitement, as well as some tough moments, through a series of photos and videos.

During one clip, Sailor panned the camera down toward her as she sat on the hardwood floor and massaged her calf with a foam roller. “Dancing is the hardest thing I’ve ever done with my body,” she wrote beneath the clip.

Image zoom Sailor Brinkley-Cook

In another video, Chmerkovskiy, 33, recorded himself in the mirror dancing to “Say My Name” by Destiny’s Child before panning the camera over to his partner, who remained in the same position on the floor.

Though she appeared tired and sore as she foam-rolled her leg, Sailor was still game to join in with the song and began singing to the R&B tune.

“I feel like we’re on American Idol, not Dancing with the Stars,” a voice can be heard jokingly saying in the background.

Image zoom Sailor Brinkley Cook/Instagram

Image zoom Sailor Brinkley Cook/Instagram

Above the video, which was initially shared to Chmerkovskiy’s Instagram Stories, Sailor excitedly wrote, “STUUUU day TWOOOO!”

Other videos from earlier in the week showed Sailor in an all-gray ensemble preparing for her rehearsal with Chmerkovskiy and dancing around.

“BACK IN DA STUUU!” she wrote across one snap, while another read, “Feeling graceful AF”

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Image zoom Sailor Brinkley-Cook

Christie’s nasty fall last week left her with multiple broken bones, which required surgery to insert a plate and screws to repair her shattered arm. The supermodel also dislocated her wrist and, on top of that, had already twisted her ankle earlier in practice.

Knowing she would be unable to compete, Christie, 65, requested that her daughter fill her spot and luckily, Sailor rose to the challenge — though she wasn’t initially sold on joining the show.

“I didn’t want to at first, honestly,” Sailor told PEOPLE. “I was terrified. It was a very scary thing for me. The whole idea of having to be live on stage, be on TV dancing, that’s something I’ve never done before.”

“I was so scared, but that was the reason I had to do it,” she continued. “I had to surpass the fear. I had to be stronger than the things that scare me.”

“[My mom] told me to have fun with it and to not let fear stop me from doing any of it,” Sailor added.

Image zoom Sailor Brinkley-Cook Allen Berezovsky/Getty

During the premiere, Sailor donned a white, floor-length gown, which was the same one designed for her mother, as she danced the foxtrot to Billy Joel‘s “Uptown Girl.”

“Sailor is truly one fearless, strong, amazing person who just always impresses me,” Christie told PEOPLE before the premiere.

And her pro partner shared the same sentiment.

“Obviously it was a very extraordinary situation, but it wouldn’t be Dancing with the Stars without a little excitement,” Chmerkovskiy told PEOPLE. “In 15 seasons, I’ve never had an experience like this.”

Still, he said, “I’m glad I did. I’m glad I was the one that was put in this position. I’m really grateful for the challenge and I’m grateful I got to share it with an awesome person like Sailor.”

Image zoom Tom Bergeron, Christie Brinkley, Sailor Brinkley-Cook and Val Chmerkovskiy Eric McCandless/ABC

While her mom copes with the physical recovery of her surgery and the emotional fallout of not being able to compete, Sailor has her eyes on the prize — and for a very special reason.

“I’m doing this mostly for my mom!” she said during the premiere. “I just want to make her happy and make her proud.”