Sister staying for the summer...

Miriam
My husband and I have payed for my 12 year old little sister to come out and spend the summer out with us in Hawaii! 
I'm crazy excited. I want this to be fun for her, but still give her responsibility. 
Maybe like chores or jobs to do to help mature her. I don't want her going back home and having a hard time getting back in the routine.
Of course, l don't want her to have to do work the whole time she's here! We will be doing a LOT of other fun things while she's here. too. :)
Has anyone else had someone come stay the summer with them? How was your experience? What did you make them do to "earn their stay"?