Kim Zolciak-Biermann has one rule for her girls when it comes to lip fillers: You've gotta wait until you're officially an adult. She was that way with her eldest daughter, Brielle Biermann, who has told The Lookbook, "I started getting my lips done right when I turned 18." Kim even took Brielle out to L.A. to get her lips done, reasoning, "I got a lot of heat for that, but it’s like, she’s going to do it anyway.”

That same rule was in place for Ariana Biermann too. Kim just explained that her high school senior couldn't wait until her 18th birthday so she could get a little lip filler. "Well, she's 18 now, so it was like, 'Do it!'" Kim told ET during BravoCon on November 15. "I think she's been dying to be 18 so that she could do something like that or do her lips or do whatever – she's been dying to be 18." 

Kim and Brielle's plumped pouts may have influenced Ariana. "She's blessed in that arena, but, you know, after watching Brielle and I, she's probably a little bit more motivated," Kim told ET. "But I'm like, 'You're 18.' Until you're 18 you can't do anything and that's kind of been the rule in my house, so she turned 18 a month ago, so we're doing OK."

Kim also got into the backstory of how Ariana ended up wearing Kim's skimpy Playboy bunny costume for Halloween, and why it might be hard for fans to recognize that Ariana is all grown up and an adult now. 

"She's been on camera since she was four years old," Kim said. "She was four on Real Housewives of Atlanta... and she had a Halloween party and she was like, 'Mom, I need one of your costumes, like, what am I going to do?' And I was like, 'I don't know. What do you want? I don't really dress up, sweetie. All I have is that Playboy costume,' and she's like, 'I'll try it,' and it worked. And so it wasn't like she had planned for it, but it worked out and she looked great in it."