EXCLUSIVE: 'Duck Dynasty's Sadie Robertson Sweetly Gushes Over New Relationship With College QB Trevor Knight

Robertson is gearing up to hit the road on her Live Original Tour.

Cute new couple alert!

While rumors surrounding Sadie Robertson and Texas A&M quarterback Trevor Knight have been swirling online, the Duck Dynasty star confirms new details about their relationship exclusively to ET.

"We've been dating for three weeks, so it's super chill," Robertson said, sitting down in ET's Burbank, California, studio on Monday. But the duo has been friendly for a few months now, popping up fairly frequently in each other's Instagram feeds.

WATCH: 'Duck Dynasty' Stars Willie and Korie Robertson Get Candid on Disciplining Kids 

"He had messaged me because he goes to Haiti every year on a mission trip and he saw that I go to Haiti," she explained. "We just kinda connected through that, very much friends at first."

Then, Sadie's best friend (and her cousin Reed Robertson's fiancee, Brighton Thompson) had to bail on a planned girls night at a Justin Bieber concert.

WATCH: Why Sadie Robertson Attended Prom With Her Cousin, Cole 

"Trevor lives in Texas and he was messaging me, and I was like, 'Uh, do you want to go to a Justin Bieber concert with me? Because I don't have anybody to go with.' And he was like, 'Sure.' So, he came and I guess we just hit it off," Sadie recalled. But not well enough, apparently, to make it official.

"We didn't date then. Actually, I didn't talk to him for a month after that. I was like, 'No,'" the 19-year-old admitted. "Then a month later he called me and was like, 'So, why didn't you just talk to me for a month?' And we ended up becoming friends and, of course, started dating three weeks ago."

Sadie's mom, Korie Robertson, gave Trevor two thumbs up when asked for her review, and Sadie said that he's already met the whole Duck Dynasty clan.

"My family's a little scary and a little intimidating -- they're big LSU fans and he plays for Texas A&M -- so that was kinda funny, but he's a good guy," she said. "Even Pepaw Phil was nice!"

WATCH: Sadie Robertson Reveals Why Her Feature Film Debut Was the 'Perfect' Part 

But when it comes to the Robertsons' reality TV fame, Trevor didn't bat an eyelash.

"Trevor has to deal with his own kinda fame -- that was weird for me," Sadie said. "We're both kinda in the spotlight ... but he does such a good job with it. He is a very strong Christian and he tells everybody about his faith, so we had a lot in common in that area."

As her new beau gears up for football season, Sadie is ready to hit the road on her Live Original Tour, bringing some of her famous family members along for the ride. Joining Sadie on her 17-city trek are John Luke and Mary Kate Robertson, Reed Robertson and Brighton Thompson, and Cole Robertson.

"It's gonna be fun, but it's also gonna be really life-changing," Sadie said. "I think people are gonna feel really inspired and leave there feeling like they can really make an impact in the world."

As for Sadie, when she's not writing books, offering inspiration to her peers, or designing her own fashion line, she's on Maid of Honor duty for Reed and Brighton.

"Brighton was just texting me like, 'We have to plan the bachelorette party!'" she said with a laugh. "We're kinda all underage, so it's probably not like most people's bachelorette parties. I think we're gonna go out to her family camp and get people to come in and do massages and stuff, so very relaxing."

WATCH: Jep and Jessica Robertson Introduce Their Newly Adopted Baby Boy 

She'll also play bridesmaid at her sister Rebecca's tropical wedding later this year. "That girl is all over the place," Sadie teased. "She finally got her bridesmaids dresses in, so that's good. We're moving in the right direction!"

Meanwhile, newlyweds John Luke and Mary Kate, who celebrated their first anniversary in June, may be holding off on taking their own next steps towards building a family.

"We're like, 'No, no, no, no, no! Slow down!'" Sadie laughed. "They have a dog, Pippa, so that's like their baby."

Live Original Tour 2016 kicks off on Sept. 22 in Allen, Texas, and will wind its way around the country before wrapping in Nashville, Tennessee, on Oct. 16. Tickets are available now. 

Watch Sadie's full interview with ET in the player below.