Stephenie Meyer, the Twilight series author gave an interview with LA Times and discussed some characters being brought to life. Here is what was said about Ashley as Alice Cullen.

Was there any one actor in the film that you came the closest to your vision for their character while you were writing Twilight?

On first look, the one that really jumped out was Ashley Greene as Alice. I saw a picture of her and just thought, ‘You found Alice! Oh my gosh!’