Kim Zolciak Posts Sweet Message in Honor of Daughter Brielle's 20th Birthday: 'I Am Extremely Proud'

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Kim Zolciak is one proud mama.

The Don't Be Tardy star took to Instagram on Saturday to share a sweet message to her oldest daughter, Brielle Biermann, in honor of her 20th birthday.

WATCH: Kim Zolciak Shares Throwback Photo, Looks Like Daughter Brielle's Twin!

Zolciak, now 38, was only 18 years old when she gave birth to Biermann, and needless to say, she can't believe how fast her daughter has grown.

"Happy Birthday to my angel @briellebiermann I just can't believe it!!!," the mother of six wrote. "I just can't believe it was 20 years ago today I became your mom! Scared out of my mind yet so excited! Had I known how easy it would have been to raise you I certainly would of had a lot less anxiety!"

"I'm extremely proud of the leader you are, the heart you have and share, the love you have for your siblings, the respect, loyalty, and commitment to your family and above it all how you always have remained TRUE to you!! Keep shining!!! Can't wait to squeeze you!! Love you oh so much!!!," she concluded. "#HappyBirthdayBrielle #TheBig20 ??????."

WATCH: Kim Zolciak's Look-Alike Daughter Brielle Flaunts Bikini Bod on Tropical Vacation

As for how Biermann celebrated the big 2-0? Well, the blonde beauty appeared to have fun traveling to Los Angeles… after mourning her teenage years.


RELATED: Brielle Biermann Defends Herself Against Plastic Surgery Rumors: 'This A** Is Not New'

Though it seems Biermann spent her birthday away from her boyfriend, Michael Kopech, the two are very much still together.

ET caught up with Biermann in October, where she gushed about the Red Sox minor leaguer, even saying she thinks "he's the one!"

See more in the video below.