The 28-year-old star covets the British actress' ''beautiful'' blonde waves and insists it looks effortless.
She told people.com: ''I've always loved her hair. It's so beautiful and easy. It looks like she rolled out of bed -- and she probably did!''
Lauren insists her hair won't grow as long as she wants it to go, even though she's tried a number of different techniques to try to get it to lengthen.
She added: ''My biggest hair mistake it was chopping it off! It's so funny.
''My hair won't grow -- my hair has not gone past this length since I cut it seven years ago to my shoulders. I've tried vitamins, I've tried everything. It just won't!''
The screen beauty - who was catapulted to the spotlight on reality show 'The Hills' - prefers a natural look and enjoys getting ready for her day.
She added: ''Day to day I don't wear a lot of makeup and my hair is kind of, you know, just waves, I definitely love getting dressed up ... but I think lower maintenance is easier. [The key is to] have fun with it, really. It shouldn't be a task ... I know that sounds silly, but you should enjoy getting ready for your day.''
The BBC drama starring Aidan Turner returns to BBC One on September 4th.