Heather Rae El Moussa is flipping out over her love for Christina Haack.

The Selling Sunset alum shared a sweet birthday tribute to her husband Tarek El Moussa’s ex-wife, proving that their friendship is structurally sound.

“Happy birthday @christinahaack !” Heather posted to Instagram July 9. “Some of the iconic moments we’ve shared these last few years.”

And the 38-year-old was especially grateful that she and Christina have been able to build such a beautiful family with Christina and Tarek’s kids Taylor, 15, and Brayden, 10; Heather and Tarek’s son Tristan, 2; and Christina and ex Ant Anstead’s son Hudson, 6.

“What a gift it is to watch our co-parenting turn into real friendship, cheering each other on in every chapter, every venture, every win!” Heather continued. “Cheers to many more celebrations.”

Alongside the sweet message, Heather shared several snaps of herself and the Flip or Flop star including one of them posing in a pool wearing matching hot pink bikinis. In another, Christina can be seen pouring Heather a glass of her Clé Cachée champagne, with the two sporting matching black and white bikinis in a photo while also applying some of Heather’s HRE lipgloss.