Charli xcx on being in L.A. for the first time: "During that time, I worked with Ariel Rechtshaid… We would do things like go to Pinkberry, which was so exotic to me. I never had froyo before. And then, because I was 16…I couldn’t really go out. So we would go to a lot of house parties. And that was a very foreign thing because in the U.K., especially when I was in school, that kind of culture of like hopping around and driving around the city late and going from house party to house party was not really a thing."