Who are you thinking of?? I am thinking of Chloë Moretz,she is 16 and is good at doing stunts and all that,i think she would suit your role,though i don't like her,she is not my type!
Also Keira Knightley,only the age thing and the hair colour!
Kristen Stewart maybe(I thought she was a piece of **** until i saw her movie Snow White and the huntsman) that changed my view about her! Her age as well and hair color are not suiting to the description you gave,Chloë Grace Moretz for sure 100% in my opinion!
Bella Throne maybe,not sure!
Maybe Jennifer Lawrence as well, but i think she has black hair!
Chloë Grace Moretz would suit 100%!!