During the painting scene (around 22:19) There are paintings behind Alicia and Claire. One of them is clearly a reference to the Korean Pop group Wonder Girls, and their debut single "Irony".
When Massie and the rest of their clique are walking down the hall, Massie's earrings are both clearly secured. Later on, she concluded that she lost it before, while they were outside or in the Range Rover.
When The Clique are in the car discussing "Glambition" the detail on Massie's headband switches sides when the camera goes from looking at her from the front to a side view.