Carla, the leaked name from a while ago was originally thought to be the mysterious lady in red by many. However if you watch the new e3 trailer and pause at the part where Ada looks through some files, you see Carla's picture, her name, and another photo of her and that new doctor antagonist, Dr. Simmons. I believe she is the original test subject of the J'aivo (sp) since you see her name in the video tape from the last trailer which shows a Jaivo emerging from its cocoon. I'm guessing she won't actually play a big role but is probably back story to how the new virus was developed. She looks to be the wife of Dr. Simmons judging by one of the photos.
Also, the trailer has a snippet of a conversation between Simmons and Ada where he says he is going to frame her for all the bio-terrorist outbreaks. I guess she WON'T be the villian mastermind in this game but instead works under Simmons & Neo-Umbrella only to be framed and back stabbed. Chris wants vengeance against her since she kills his BSAA team but Leon wants to keep her alive because she'll be a key witness against Simmons.
It's pretty obvious that Dr. Simmons is the main antagonist this time and he is trying to rebuild Umbrella or something. Also I believe this new virus is what clara has and like a the name suggest it change like the buttterfly, maybe carla can shapeshift and change into people with this virus ???