In 2008, her laid back look is definitely a dramatic change to the Woman we know today in her beautiful Zuhad Muhair dress!
Los Angeles premier for Twilight 2008:

Even then Kristen has a edge to her! The casual number works perfectly to accompany the character Bella in the first book, youthful and innocent.
Los Angeles premier for New Moon 2009:

Kristen's look here is very much vampire-esk which ties into the whole saga. We can see here that she is developing a more edgier style but still retaining her innocent look.
Love the detailing on the dress with the sparkles!
Los Angeles premier for Breaking Dawn 2010:
Kristen's look here is ooozing with sex appeal. With this full length dress with the thigh cut hints SO much at glamour combined with a vintage vampire look with the purple glitter, Kristen looks amazing.
Los Angeles premier for Breaking Dawn Part Two 2012:

As ever Kristen is being talked about, whether it's her relationship with Robert Patterson or what she is wearing.
This number spark controversy when you could see her bum.
The cream corset dress shouts gorgeous to me and I think the twilight star looks glam!
Check out the Breaking Dawn Part two official trailer
What's your favourite Kristen look?