The fifth and final new fighter to be added to the upcoming Ultra Street Fighter IV will be Decapre. She's new, while also being not new. It's weird.
She's not a new character, having first appeared briefly in Street Fighter Alpha 3 as an NPC (which you can see in the intro to the video below). But she is new as a playable fighter, and has a pretty great name, though I will now and forever know her as Evil Cammy.
Here's Capcom's excited description:
Making her first brief appearance in a Street Fighter game as a non-playable character in Street Fighter Alpha 3, where she was seen as one of M. Bison's Dolls, Decapre now joins the fight! Although a partial mask hides a giant burn mark located on this Russian beauty's face, challengers will be scarred by her quick and elusive scramble moves as well as her psycho power infused attacks, which allow her to share her pain with her opponents.