From Michael Bay’s Official Website:
I would like for all you S4TE best hunting knife fans to welcome Rosie Huntington Whitely to the world of Transformers. As some of you might know, she’s the new female lead in Transformers 3.
Victoria’s Secret model Rosie Huntington-Whiteley has worked with film director Michael Bay before on his Victoria’s Secret “A Thousand Fantasies” ad. Replacing Megan Fox as the female lead shouldn’t be much of a challenge anyway, since I highly doubt that real acting skills are required for the female lead in the third Transformers movie.