This is The Khaleesi in her light blue dress that you might find her in while upon her throne. This cosplayer wears a light blue chiffon or light cotton dress.
She also is wearing a khalisi-style wig (Or extensions?) with the signature braid around the crown. This is a simple and sexy look that is great for parties.
If you are looking to diy, Yaya Han has a nice writeup of her costume.