Brielle didn't elaborate on the mishap; she simply whispered the news to sister Ariana Biermann under her breath while filming a joint confessional for their family's reality show. But TooFab did some further investigating and spoke to Brielle personally.
"Oh, my God! They aired that?!" she said candidly over the phone. "F--k! Oh, my God. I'm so embarrassed right now, I'm gonna cry!" She playfully yelled at her publicist, who was also on the call, for not giving her the heads up.
"Yes, he did walk in on me once. Yes, yes," Brielle eventually confirmed. "His rule was like, 'I don't give a f--k what you do, just not in my house.' But he was so strict in high school! Even after I turned 18, I couldn't do anything. I had a curfew at like 6 p.m. on school nights. I get out of school at 4, which means I can go to Chick-fil-A and come home."
"I had a boyfriend, and he -- I don't know. We were stupid. We were being stupid," she added. When we asked if her partner in crime was then-boyfriend Michael Kopech, Brielle paused before saying, "No, I'm not saying who -- but I'm sure you can figure it out."
When we asked Kim about the ordeal, her reaction was a bit less boisterous. "Brielle's an adult. [Kroy] was unaware that she was around, so it was a sheer accident," she said. "It was a very lighthearted situation that happened; although, he will kind of bust her chops here and there about it."
"Kroy made jokes for the first month!" Brielle told us. "I was like, 'Dude, you're f--king gross.' And you know what's weird? My birthday was a few weeks later, and he had just ordered my Jeep that morning. After my mom told me, she was like, 'He could've f--king killed you! He was so pissed.'"
Both Kim and Brielle also told us how proud they were of how far Ariana had come since the season premiere of "Don't Be Tardy." Ariana and then-boyfriend Colin broke up, which actually prompted a lifestyle change for the 17-year-old.
"She's lost 30 pounds," Kim told us. "She's kind of come into her own, and she's working out all the time! She's really feeling great about herself. Either way, she's a very beautiful person on the inside, and she knows that that's really all that matters. She's a straight-A student, she's an incredible sister, she has so many great attributes. And I think she's beautiful."
When asked if the split was hard on the family given how much they liked Colin, Kim said no.
"I want my daughter to do what makes her happy at the end of the day, and if it's not Colin then we just keep it moving," she said. "I'm here for my kids, honey -- not for Colin. But he's a good guy."
Brielle said Ariana used to hate taking photos next to her because she felt self-conscious about her body. Laughing, Brielle told us the tables had turned.
"We went to an event recently together, and she always says she doesn't wanna take photos with me because she thinks I'm prettier, and I'm like, 'Dude, we're gonna have no photos when we're 30, 40, 50. This is insane. Just take the f--king photo,'" Brielle explained. "But at the event, I was like, 'I understand because you look so cute right now, and I actually don't wanna take a photo with you.'"
"I think that the breakup definitely made her -- I think she was so sad over the breakup that she just didn't eat as much or eat as often, and doing that, she lost a lot of weight," Brielle continued. "And now that she's lost so much weight, we go to dinner, and she's like doing portion control shit! And I'm like, 'F--k, dude. Just eat the whole burger, please. You're making me feel like a fatass!' She's like, 'I don't wanna get fat again.' I'm like, 'You were never fat! Stop!'"
As far as her own split from Chicago White Sox pitcher Michael Kopech, Brielle previously told TooFab, "It was more of him wanting to take a break, and he wanted me to wait on him. And I was like, 'I'm not gonna wait on you, dude. You clearly wanna go f--k around. You think I'm stupid? I'm not stupid. I'm not gonna be waiting for you to return. I have a life, too.' He was like, 'In a year, we can date.' I was like, 'Are you insane? No.'"
She's admittedly in a much better head space today than she was when the couple first split, around March of last year.
"It needed to happen," she explained of the relationship she once saw ending in marriage. "I just was a little in denial because no one's ever left me before. So I was like, 'What the f--k is your problem? You have issues to leave me.' I was so confused at the time. I was like, 'Really? You're really leaving me? Okay, bye!' I was such an asshole."
Brielle also confirmed she has officially moved out of Kim and Kroy's Atlanta mansion, "but you'll have to wait and see how it actually ends up playing out because it's definitely a little different situation."