"She did a reality show [before], so I was shocked that she said yes to it, because it's like you're mic-ed for everything," said Jessica, referring to her sister's MTV reality series, The Ashlee Simpson Show, which ran for two seasons from 2004 to 2005.
"[I asked her], 'Wait, are you sure you want everything to be out there?' And she's like, Yeah, I'm really confident,'" the 38-year-old actress and businesswoman recalled. "That's what you have to have when you're doing reality, you know? You have to be confident in who you are and what you're standing for, and I think she is."
As for Jessica herself -- who starred in the infamous MTV reality series Newlyweds: Nick and Jessica, which followed her marriage to ex-husband Nick Lachey for three seasons from 2003 to 2005 -- she has no interest in headlining another reality series about her life ever again.
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"Oh, gosh no," she quickly replied when asked about the possibility. "I am confident, but I also know how people can take your words and make them whatever they want to make them."
However, that doesn't mean she's not going to be stopping by during the course of her sister's show. Jessica said she will be appearing in some episodes "toward the end," and stressed that the series is about Ashlee and Evan's "journey together, and discovering music together, which is awesome."
"She's out there singing again, which I couldn't be more proud of," Jessica said of her 33-year-old sister, who shares a 2-year-old son, Jagger, with Evan, and is also mom to 9-year-old son Bronx Mowgli, from her previous marriage to rocker Pete Wentz.
According to Jessica, she and her sister are both going to be making a return to performing.
"We've done a lot of behind-the-scenes-type work, because we've become mothers, but now we're going back to the stage, for both of us," she teased. "The stage is my home, so I look forward to being on it."
Meanwhile, she's also built a flourishing beauty product and cosmetics line, Beauty Fiend, which she was promoting at this year's Beautycon LA -- where she was joined by her daughter.
Looking at her new line of Beauty Fiend makeup brushes and cosmetic accessories, the multihyphenate celeb marveled at how her life and goals have developed and blossomed in the last few years.
"I never imagined I would have makeup brushes; I use them every day, but I never thought my name would be on them," Jessica explained. "I just think, really, it's all about not even just believing in all of your dreams [but also] knowing that the unknown dreams can come true."