It all kicked off on when Kendall appeared as a guest on big sister Khloe Kardashian's new show Kocktails With Khloe, which featured a discussion on Farrah's feud with Nicki Minaj.
(That row happened when Nicki took to Twitter after watching Teen Mom reruns to say she didn't like the way Farrah spoke to her mother.)
Kendall, 20, has said: "I don't really agree with a lot of Farrah's decisions in life. That's why I'd say I'm on Nicki's side."
Khloe also said she was Team Nicki.
Now, we all know former Celebrity Big Brother housemate Farrah is rather feisty and doesn't hold back, so it's no surprise she responded to Kendall's comments via Twitter.
Farrah tweeted a picture of an old Kardashian Christmas card that had been Photoshopped to insert an image of Kim Kardashian's ex-boyfriend Ray J, with whom she made a sex tape.
The card featured the words: "I made this whole family famous with my d**k."
Farrah added the caption: "#LifeChoies @KendallJenner."
So far Kendall hasn't replied.
Watch this space.