GameSpot has posted an exclusive vignette of Mileena that delves into her origin:
Mileena was created by Shang Tsung in his foul flesh pits. Twisted and mad, she's equally beauty and beast. Devoid of a conscience, she has the rage of a wild animal. Only the evil lord Shao Kahn possesses the will to control her. Determined to destroy her rival Kitana, Mileena entered the Mortal Kombat tournament, ready to butcher anyone and everyone who gets in her way.


The vignette also mentions that the games' soundtrack is coming to stores in April 2011. Thanks go to user for the word on this update!

Update: The official Mortal Kombat Community Manager posted a longer preview of Mileena's theme song here.