The model and actress, 26, hit back at the singer, 25, after he made some comments about her she didn't appreciate while appearing on "The Late Late Show with James Corden" this week.
Corden, while playing the game of "Spill Your Guts or Fill Your Guts," asked Bieber to rank wife Hailey Baldwin's famous friends from his most favorite to least favorite. Thes list included Gigi Hadid, Cara Delevingne and Kendall Jenner.
Bieber admitted that he's closest to Jenner, then Hadid, then Delevingne only to explain his ranking a few seconds later after getting slack from the audience.
"So Kendall's the favorite?" asked Corden. "I haven’t spent a lot of time with Gigi and I haven’t spent a lot of time with Cara so I have nothing against those people," Bieber responded.
"It’s just I have a better relationship [with Kendall]. It’s not like I’m like ugh, screw Cara, screw her, you know what I mean? OK," he added.
Delevingne took to social media to express herself.
"Now vs. Then... If you have nothing against me, then why don't you unblock me? Love you @haileybieber - he should have just eaten the bull penis," she wrote on Instagram alongside two photos -- one when Bieber performed at Victoria's Secret fashion show and another of them at a hockey game.
Her clap back has gotten praise on Twitter. "NOT CARA DELEVINGNE DRAGGING JUSTIN," a fan wrote.
"CARA DELEVINGNE JUST ENDED JUSTIN BIEBER AND HIS WIFE," said another.
"In this house we decide to stan Cara Delevingne," someone else pointed out.
This isn't the first time Delevingne held Bieber accountable for his words. Last July, she defended Taylor Swift after Bieber posted a message to the Grammy-winner during the Scooter Braun/Big Machine Records controversy.
"Gentleman? @haileybieber @justinbieber you must be bored," she wrote in the comments section, according to Teen Vogue. "I wish you spent less time sticking up for men and more time trying to understand women and respecting their valid reactions.
"As a married man, you should be lifting women up instead of tearing them down because you are threatened. I am not sure you actually understand what an apology is. This issue that @taylorswift is talking out is about far more than a picture and you know that. As you said, you haven't spoken to her in years, which means you definitely don't understand the situation. I do. Take a step back and try and learn from this. We should all be on the same team. End of story."