what to use to get Keira Knightley Short Hair?

my sister is a real follower of the way celebrity make up their hair and i know exciting and funky these hairdos can make you look.so now when she saw kiera knightley in domino she was totally enchanted by the eccentric way in which she had cut her hair ,she has  shoulder length hair which is trimmed and now wants to change in to the kiera knightley look.in what way can you get the Keira Knightley Short Hair with the same pattern and styling that suited her character in that movie?do i need to use any hair serum or i can use some water ?also is there any hairstylist that can offer some insight on what needs to be done to get the Keira Knightley Short Hair look.?