Here is the size chart that I got from American Eagle.
Women's Tops, Bottoms, Underwear and Swimwear Women's Sizes XS S M L XL XXL No. Size 0-2 4-6 8-10 12 14 16-18 Bust (in inches) 31-32 33-34 35-36 37½ 39 40½-42 Cup Size A B C C-D D D Waist (in inches) 23-24 25-26 27-29 30-31 32-33 33½-34½ Hip (in inches) 33-34 35-36 37-38 39 40 42-44½ Torso (in inches) 54-55 56-57½ 58-59½ 60-61½ 62-63 63-64
I would say a medium. I havnt found my tape measure, but I believe the waist is about 30, but you dont really wear this on your waist, it would lay lower.