It's really more of a light beefing than a feud.
In July, Cara Delevingne was deemed "awkward" for not being peppy enough toward her condescending interviewers on Good Day Sacramento. The whole thing was entirely cringe-y, and you can catch yourself up on the interview and ensuing Twitter analysis here.
The one thing that was never settled, though, was what Robb Stark from Game of Thrones thought about the whole situation. People were like, "Sure, the news anchors clearly didn't understand Cara Delevingne's dry sense of humor, and it was definitely inappropriate to imply she might not have read the book her movie was based on. But when will Robb Stark from Game of Thrones give his input?" Finally, we can put our minds at ease. Robb Stark, who apparently is an actor named Richard Madden, told Style:
"It was unprofessional. It made her seem ungrateful. She showed her age. For Cinderella, I did six weeks of those interviews, where you get asked the same eight questions. If you're not capable of doing that gracefully, then don't do it."
Thanks so much for your input, Richard Madden. After your famously smooth press tour for Cinderella, you're basically the preeminent expert on the professionalism levels of all celebrities. Plus, due to how impressively old you are, you definitely know more than all younger people, who are always lamely showing their age. Especially when they stand up for themselves!