Carey Mulligan does not age. She has looked young and beautiful for years and it has a lot to do with her makeup choices. Rather than wearing heavy, dramatic makeup, Carey opts for a clean, dewy face with berry lips of varying shades and a small bit of eyeliner on her top lid.
The point of her makeup is to highlight her radiant skin and adorable small smile - her look is ideal for girls with small faces and features (nose, eyes, lips, etc)
Check her out in The Great Gatsby, Never Let Me Go, and An Education.
I attached a Carey Mulligan makeup tutorial as well :)