Originally Posted by SterlingDee
I think they have always planned to reveal Jean in some of the advertising. They probably revealed her so early (in the tweaser to the teaser!) because they wanted to get any buzz/discussion of her appearance out of the way before the real marketing for the film began. Her appearance adds a bit of intrigue to the film and marketers love playing up any romance angle they can in trailers because they think it appeals to female audiences.
Yea, that and they need to get across that its a sequel to the last stand, and not Origins. I would bet more than half of the general audience would think this movie is a direct sequel to Origins. With jean being in tv spots and trailers, that puts the idea to rest, while not revealing too much.