Bristowe also opens up to ET about standing up to the trolls and focusing on what matters.
"Last night I used the foot bath that she gave me. It's like, an ice bath and I just loaded that thing up with ice. I was like, 'Oh this is gonna feel so good,'" Bristowe said in an interview with ET's Lauren Zima this week. "I don't know if you've ever tried an ice bath, but the worst thing I've ever done. But she gave me the ice bath."
Brown took home the mirrorball trophy on season 28 of DWTS last fall with pro dancer Alan Bersten. Bristowe, who makes her debut on the ABC dancing competition on Monday, said she's soaking up all the advice she can get.
"[Brown] said the same thing as everyone else, 'Enjoy it. It goes by so fast.' So, even every blister on my foot, I look at with love right now. I'm like, 'Hey you, you're doing what you're supposed to be doing.'"
Competing on Dancing With the Stars has been a longtime dream for Bristowe, who was originally supposed to appear on the show following her Bachelorette season in 2015. In June, Chris Harrison surprised her with the news she'd be on DWTS' upcoming 29th season, months before the rest of the celebrity cast was revealed.
Bristowe thus had time to hit the gym in preparation -- though she said it hasn't been much of an advantage.
"People keep saying, 'Does Kaitlyn have an advantage from knowing and from dancing and all these things?' I actually feel I have a disadvantage in a way, because I am unlearning everything I thought I knew about dance," she shared. "It's been way more challenging than I thought."
The Off the Vine podcast host is also challenged by her first dance. "There's a lot going on and I thought my hips could move the way I want them to, but it turns out they can't," she laughed. "But I'm obsessed with the song."
Bristowe has gone through all of the emotions lately, from excitement to defeat. She shared on Instagram last weekend that she cried it out after reading mean comments about her appearance.
"I was just so mentally drained and I was tired and I was hormonal, and it was just like, anything was going to set me off. So, I took my moment. I cried for like, an hour," she told ET. "I felt all my feelings, and I don't like to stay there long. I just like to bounce back and remember that I'm living my dream right now and that nothing should get to me like that."
"When it's that time of the month I’m just gonna stay off social media," she joked of how she's going to rally against criticism every week on DWTS. "But I think being so removed from being on a show for so long, you kind of forget how nasty people can be. You just have to ignore the ones that are trying to get you down, because there are so many nice people that are trying to build you up."
In addition to her physical transformation, Bristowe has also been going to therapy and "working on myself." She credits her boyfriend, Jason Tartick, for helping keep her focused on what matters.
"Jason's the kind of guy that everything kind of bounces off of him. He doesn't understand like, feeling your feelings, so [when I'm crying], he's looking at me like, 'What, are you nuts? Like, you're literally on Dancing With the Stars and you've worked so hard and you've got all this stuff going on,'" she said. "I was like, 'Oh, reality check. I like that.'"
The all-new season of Dancing With the Stars premieres Monday, Sept. 14 at 8 p.m. ET/PT on ABC. In the meantime, tune into Entertainment Tonight on Thursday for more from Bristowe.